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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def EnumValueName(self, enum, value):
 """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. """

    return self.enum_types_by_name[enum].values_by_number[value].name