Setter for **self.__functions** attribute.

        :param value: Attribute value.
        :type value: tuple

def functions(self, value):
        """
        Setter for **self.__functions** attribute.

        :param value: Attribute value.
        :type value: tuple
        """

        if value is not None:
            assert type(value) is tuple, "'{0}' attribute: '{1}' type is not 'tuple'!".format("functions", value)
            for element in value:
                assert type(element) is LibraryHook, "'{0}' attribute: '{1}' type is not 'LibraryHook'!".format(
                    "functions", element)
        self.__functions = value