text: #!/usr/bin/python -u
  import libxml2
  import sys
  
  ARG = 'test string'
  
  class ErrorHandler:
  
      def __init__(self):
          self.errors = []
  
      def handler(self, msg, data):
          if data != ARG:
              raise Exception("Error handler did not receive correct argument")
          self.errors.append(msg)
  
  # Memory debug specific
  libxml2.debugMemory(1)
  
  schema="""<?xml version="1.0"?>
  <element name="foo"
           xmlns="http://relaxng.org/ns/structure/1.0"
           xmlns:a="http://relaxng.org/ns/annotation/1.0"
           xmlns:ex1="http://www.example.com/n1"
           xmlns:ex2="http://www.example.com/n2">
    <a:documentation>A foo element.</a:documentation>
    <element name="ex1:bar1">
      <empty/>
    </element>
    <element name="ex2:bar2">
      <empty/>
    </element>
  </element>
  """
  
  valid="""<?xml version="1.0"?>
  <foo><pre1:bar1 xmlns:pre1="http://www.example.com/n1"/><pre2:bar2 xmlns:pre2="http://www.example.com/n2"/></foo>"""
  
  invalid="""<?xml version="1.0"?>
  <foo><pre1:bar1 xmlns:pre1="http://www.example.com/n1">bad</pre1:bar1><pre2:bar2 xmlns:pre2="http://www.example.com/n2"/></foo>"""
  
  rngp = libxml2.relaxNGNewMemParserCtxt(schema, len(schema))
  rngs = rngp.relaxNGParse()
  ctxt = rngs.relaxNGNewValidCtxt()
  e = ErrorHandler()
  ctxt.setValidityErrorHandler(e.handler, e.handler, ARG)
  
  # Test valid document
  doc = libxml2.parseDoc(valid)
  ret = doc.relaxNGValidateDoc(ctxt)
  if ret != 0 or e.errors:
      print("error doing RelaxNG validation")
      sys.exit(1)
  doc.freeDoc()
  
  # Test invalid document
  doc = libxml2.parseDoc(invalid)
  ret = doc.relaxNGValidateDoc(ctxt)
  if ret == 0 or not e.errors:
      print("Error: document supposed to be RelaxNG invalid")
      sys.exit(1)
  doc.freeDoc()
  
  del rngp
  del rngs
  del ctxt
  libxml2.relaxNGCleanupTypes()
  
  # Memory debug specific
  libxml2.cleanupParser()
  if libxml2.debugMemory(1) == 0:
      print("OK")
  else:
      print("Memory leak %d bytes" % (libxml2.debugMemory(1)))
      libxml2.dumpMemory()
  
  