def validate(cls, value):
        """Validate that the specified value is a valid enum.

        This method will raise a ValueError if the value is
        not a valid enum.

        :param value: the string value to verify
        """
        if value not in cls.VALUES:
            raise ValueError(
                f"Invalid ParameterSource value: {value!r}. Valid"
                f" values are: {','.join(cls.VALUES)}"
            )
Validate that the specified value is a valid enum.

        This method will raise a ValueError if the value is
        not a valid enum.

        :param value: the string value to verify
        
dynaconf/vendor/click/core.py