code: def add_prefix(self, prefix, uri):
          
          root = self.wsdl.root
          mapped = root.resolvePrefix(prefix, None)
          if mapped is None:
              root.addPrefix(prefix, uri)
              return
          if mapped[1] != uri:
              raise Exception('"%s" already mapped as "%s"' % (prefix, mapped))
docs: Add I{static} mapping of an XML namespace prefix to a namespace.
          This is useful for cases when a wsdl and referenced schemas make heavy
          use of namespaces and those namespaces are subject to changed.
          @param prefix: An XML namespace prefix.
          @type prefix: str
          @param uri: An XML namespace URI.
          @type uri: str
          @raise Exception: when prefix is already mapped.