code: def getExtensionArgs(self):
          
          aliases = NamespaceMap()
  
          required = []
          if_available = []
  
          ax_args = self._newArgs()
  
          for type_uri, attribute in self.requested_attributes.items():
              if attribute.alias is None:
                  alias = aliases.add(type_uri)
              else:
                  # This will raise an exception when the second
                  # attribute with the same alias is added. I think it
                  # would be better to complain at the time that the
                  # attribute is added to this object so that the code
                  # that is adding it is identified in the stack trace,
                  # but it's more work to do so, and it won't be 100%
                  # accurate anyway, since the attributes are
                  # mutable. So for now, just live with the fact that
                  # we'll learn about the error later.
                  #
                  # The other possible approach is to hide the error and
                  # generate a new alias on the fly. I think that would
                  # probably be bad.
                  alias = aliases.addAlias(type_uri, attribute.alias)
  
              if attribute.required:
                  required.append(alias)
              else:
                  if_available.append(alias)
  
              if attribute.count != 1:
                  ax_args['count.' + alias] = str(attribute.count)
  
              ax_args['type.' + alias] = type_uri
  
          if required:
              ax_args['required'] = ','.join(required)
  
          if if_available:
              ax_args['if_available'] = ','.join(if_available)
  
          return ax_args
docs: Get the serialized form of this attribute fetch request.
  
          @returns: The fetch request message parameters
          @rtype: {unicode:unicode}