Returns a string containing the name of an enum value.

def Name(self, number):
    """Returns a string containing the name of an enum value."""
    if number in self._enum_type.values_by_number:
      return self._enum_type.values_by_number[number].name
    raise ValueError('Enum %s has no name defined for value %d' % (
        self._enum_type.name, number))