def __get_constants(self):
        """
        Gets the constants from the class that acts like a namespace for constants and adds them to the replace pairs.
        """
        helper = ConstantClass(self._constants_class_name, self._io)
        helper.reload()
        constants = helper.constants()

        for name, value in constants.items():
            self._add_replace_pair(name, value, True)

        self._io.text('Read {0} constants for substitution from <fso>{1}</fso>'.
                      format(len(constants), helper.file_name()))
Gets the constants from the class that acts like a namespace for constants and adds them to the replace pairs.