code: def get_attribute(self, name):
          
          for child, ancestry in self.attributes():
              if child.name == name:
                  return (child, ancestry)
          return (None, [])
docs: Get (find) a I{non-attribute} attribute by name.
          @param name: A attribute name.
          @type name: str
          @return: A tuple: the requested (attribute, ancestry).
          @rtype: (L{SchemaObject}, [L{SchemaObject},..])