diff -r a80a66ba52d6 -r 9f6f46dbe3ae xmlclass/xsdschema.py
--- a/xmlclass/xsdschema.py	Fri Oct 28 13:06:52 2022 +0800
+++ b/xmlclass/xsdschema.py	Fri Oct 28 14:07:13 2022 +0800
@@ -23,16 +23,11 @@
 # Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
 
 
-
-
 import os
 import re
 import datetime
 from types import FunctionType
 from xml.dom import minidom
-from future.builtins import round
-from six import string_types
-from past.builtins import int
 
 from xmlclass.xmlclass import *
 
@@ -170,7 +165,7 @@
 
     if typeinfos["type"] in ["restriction", "extension"]:
         # Search for base type definition
-        if isinstance(typeinfos["base"], string_types):
+        if isinstance(typeinfos["base"], str):
             basetypeinfos = factory.FindSchemaElement(typeinfos["base"], SIMPLETYPE)
             if basetypeinfos is None:
                 raise "\"%s\" isn't defined!" % typeinfos["base"]
@@ -394,7 +389,7 @@
 
     elif typeinfos["type"] == "list":
         # Search for item type definition
-        if isinstance(typeinfos["itemType"], string_types):
+        if isinstance(typeinfos["itemType"], str):
             itemtypeinfos = factory.FindSchemaElement(typeinfos["itemType"], SIMPLETYPE)
             if itemtypeinfos is None:
                 raise "\"%s\" isn't defined!" % typeinfos["itemType"]
@@ -440,7 +435,7 @@
         # Search for member types definition
         membertypesinfos = []
         for membertype in typeinfos["memberTypes"]:
-            if isinstance(membertype, string_types):
+            if isinstance(membertype, str):
                 infos = factory.FindSchemaElement(membertype, SIMPLETYPE)
                 if infos is None:
                     raise ValueError("\"%s\" isn't defined!" % membertype)
@@ -514,7 +509,7 @@
     attrnames = {}
     if base is not None:
         basetypeinfos = factory.FindSchemaElement(base)
-        if not isinstance(basetypeinfos, string_types) and basetypeinfos["type"] == COMPLEXTYPE:
+        if not isinstance(basetypeinfos, str) and basetypeinfos["type"] == COMPLEXTYPE:
             attrnames = dict([(x["name"], True) for x in basetypeinfos["attributes"]])
 
     for element in elements:
@@ -815,7 +810,7 @@
                 raise ValueError("Only group composed of \"choice\" can be referenced in \"choice\" element!")
             choices_tmp = []
             for choice in elmtgroup["choices"]:
-                if not isinstance(choice["elmt_type"], string_types) and choice["elmt_type"]["type"] == COMPLEXTYPE:
+                if not isinstance(choice["elmt_type"], str) and choice["elmt_type"]["type"] == COMPLEXTYPE:
                     elmt_type = "%s_%s" % (elmtgroup["name"], choice["name"])
                     if factory.TargetNamespace is not None:
                         elmt_type = "%s:%s" % (factory.TargetNamespace, elmt_type)
@@ -849,7 +844,7 @@
                 raise ValueError("Only group composed of \"sequence\" can be referenced in \"sequence\" element!")
             elements_tmp = []
             for element in elmtgroup["elements"]:
-                if not isinstance(element["elmt_type"], string_types) and element["elmt_type"]["type"] == COMPLEXTYPE:
+                if not isinstance(element["elmt_type"], str) and element["elmt_type"]["type"] == COMPLEXTYPE:
                     elmt_type = "%s_%s" % (elmtgroup["name"], element["name"])
                     if factory.TargetNamespace is not None:
                         elmt_type = "%s:%s" % (factory.TargetNamespace, elmt_type)
@@ -2215,7 +2210,7 @@
         "facets": STRING_FACETS,
         "generate": GenerateSimpleTypeXMLText(lambda x: x),
         "initial": lambda: "",
-        "check": lambda x: isinstance(x, string_types)},
+        "check": lambda x: isinstance(x, str)},
 
     "normalizedString": {
         "type": SIMPLETYPE,
@@ -2224,7 +2219,7 @@
         "facets": STRING_FACETS,
         "generate": GenerateSimpleTypeXMLText(lambda x: x),
         "initial": lambda: "",
-        "check": lambda x: isinstance(x, string_types)
+        "check": lambda x: isinstance(x, str)
     },
 
     "token": {
@@ -2234,7 +2229,7 @@
         "facets": STRING_FACETS,
         "generate": GenerateSimpleTypeXMLText(lambda x: x),
         "initial": lambda: "",
-        "check": lambda x: isinstance(x, string_types)
+        "check": lambda x: isinstance(x, str)
     },
 
     "base64Binary": {
@@ -2434,7 +2429,7 @@
         "facets": NUMBER_FACETS,
         "generate": GenerateSimpleTypeXMLText(str),
         "initial": lambda: "",
-        "check": lambda x: isinstance(x, string_types)
+        "check": lambda x: isinstance(x, str)
     },
 
     "dateTime": {
@@ -2474,7 +2469,7 @@
         "facets": NUMBER_FACETS,
         "generate": GenerateSimpleTypeXMLText(str),
         "initial": lambda: "",
-        "check": lambda x: isinstance(x, string_types)
+        "check": lambda x: isinstance(x, str)
     },
 
     "gYearMonth": {
@@ -2484,7 +2479,7 @@
         "facets": NUMBER_FACETS,
         "generate": GenerateSimpleTypeXMLText(str),
         "initial": lambda: "",
-        "check": lambda x: isinstance(x, string_types)
+        "check": lambda x: isinstance(x, str)
     },
 
     "gMonth": {
@@ -2494,7 +2489,7 @@
         "facets": NUMBER_FACETS,
         "generate": GenerateSimpleTypeXMLText(str),
         "initial": lambda: "",
-        "check": lambda x: isinstance(x, string_types)
+        "check": lambda x: isinstance(x, str)
     },
 
     "gMonthDay": {
@@ -2504,7 +2499,7 @@
         "facets": NUMBER_FACETS,
         "generate": GenerateSimpleTypeXMLText(str),
         "initial": lambda: "",
-        "check": lambda x: isinstance(x, string_types)
+        "check": lambda x: isinstance(x, str)
     },
 
     "gDay": {
@@ -2514,7 +2509,7 @@
         "facets": NUMBER_FACETS,
         "generate": GenerateSimpleTypeXMLText(str),
         "initial": lambda: "",
-        "check": lambda x: isinstance(x, string_types)
+        "check": lambda x: isinstance(x, str)
     },
 
     "Name": {
@@ -2524,7 +2519,7 @@
         "facets": STRING_FACETS,
         "generate": GenerateSimpleTypeXMLText(lambda x: x),
         "initial": lambda: "",
-        "check": lambda x: isinstance(x, string_types)
+        "check": lambda x: isinstance(x, str)
     },
 
     "QName": {
@@ -2534,7 +2529,7 @@
         "facets": STRING_FACETS,
         "generate": GenerateSimpleTypeXMLText(lambda x: x),
         "initial": lambda: "",
-        "check": lambda x: isinstance(x, string_types)
+        "check": lambda x: isinstance(x, str)
     },
 
     "NCName": {
@@ -2544,7 +2539,7 @@
         "facets": STRING_FACETS,
         "generate": GenerateSimpleTypeXMLText(lambda x: x),
         "initial": lambda: "",
-        "check": lambda x: isinstance(x, string_types)
+        "check": lambda x: isinstance(x, str)
     },
 
     "anyURI": {
@@ -2554,7 +2549,7 @@
         "facets": STRING_FACETS,
         "generate": GenerateSimpleTypeXMLText(lambda x: x),
         "initial": lambda: "",
-        "check": lambda x: isinstance(x, string_types)
+        "check": lambda x: isinstance(x, str)
     },
 
     "language": {
@@ -2564,7 +2559,7 @@
         "facets": STRING_FACETS,
         "generate": GenerateSimpleTypeXMLText(lambda x: x),
         "initial": lambda: "en",
-        "check": lambda x: isinstance(x, string_types)
+        "check": lambda x: isinstance(x, str)
     },
 
     "ID": {
@@ -2574,7 +2569,7 @@
         "facets": STRING_FACETS,
         "generate": GenerateSimpleTypeXMLText(lambda x: x),
         "initial": lambda: "",
-        "check": lambda x: isinstance(x, string_types)
+        "check": lambda x: isinstance(x, str)
     },
 
     "IDREF": {
@@ -2584,7 +2579,7 @@
         "facets": STRING_FACETS,
         "generate": GenerateSimpleTypeXMLText(lambda x: x),
         "initial": lambda: "",
-        "check": lambda x: isinstance(x, string_types)
+        "check": lambda x: isinstance(x, str)
     },
 
     "IDREFS": {
@@ -2594,7 +2589,7 @@
         "facets": STRING_FACETS,
         "generate": GenerateSimpleTypeXMLText(lambda x: x),
         "initial": lambda: "",
-        "check": lambda x: isinstance(x, string_types)
+        "check": lambda x: isinstance(x, str)
     },
 
     "ENTITY": {
@@ -2604,7 +2599,7 @@
         "facets": STRING_FACETS,
         "generate": GenerateSimpleTypeXMLText(lambda x: x),
         "initial": lambda: "",
-        "check": lambda x: isinstance(x, string_types)
+        "check": lambda x: isinstance(x, str)
     },
 
     "ENTITIES": {
@@ -2614,7 +2609,7 @@
         "facets": STRING_FACETS,
         "generate": GenerateSimpleTypeXMLText(lambda x: x),
         "initial": lambda: "",
-        "check": lambda x: isinstance(x, string_types)
+        "check": lambda x: isinstance(x, str)
     },
 
     "NOTATION": {
@@ -2624,7 +2619,7 @@
         "facets": STRING_FACETS,
         "generate": GenerateSimpleTypeXMLText(lambda x: x),
         "initial": lambda: "",
-        "check": lambda x: isinstance(x, string_types)
+        "check": lambda x: isinstance(x, str)
     },
 
     "NMTOKEN": {
@@ -2634,7 +2629,7 @@
         "facets": STRING_FACETS,
         "generate": GenerateSimpleTypeXMLText(lambda x: x),
         "initial": lambda: "",
-        "check": lambda x: isinstance(x, string_types)
+        "check": lambda x: isinstance(x, str)
     },
 
     "NMTOKENS": {
@@ -2644,7 +2639,7 @@
         "facets": STRING_FACETS,
         "generate": GenerateSimpleTypeXMLText(lambda x: x),
         "initial": lambda: "",
-        "check": lambda x: isinstance(x, string_types)
+        "check": lambda x: isinstance(x, str)
     },
 
     # Complex Types