Not to be used when using numeric values.
        
        Returns
        -------
        int
            the maximal length required by this Enum to be stored in the database

def max_value_length(cls):
        """
        Not to be used when using numeric values.
        
        Returns
        -------
        int
            the maximal length required by this Enum to be stored in the database

        """
        if not hasattr(cls, '__max_value_length_'):
            cls.__max_value_length_ = max([len(c.value) for c in list(cls)])
        return cls.__max_value_length_