def EnumValueName(self, enum, value):
return self.enum_types_by_name[enum].values_by_number[value].name<EOL>
Returns the string name of an enum value.

        This is just a small helper method to simplify a common operation.

        Args:
          enum: string name of the Enum.
          value: int, value of the enum.

        Returns:
          string name of the enum value.

        Raises:
          KeyError if either the Enum doesn't exist or the value is not a valid
            value for the enum.