@abc.abstractmethod<EOL><INDENT>def has_variable_minutes(self):<DEDENT>
return<EOL>
Tests if this time system has a variable number of minutes in an hour.

        :return: ``true`` if the number of minutes per hour varies, ``false`` if the number of minutes per hour is constant
        :rtype: ``boolean``


        *compliance: mandatory -- This method must be implemented.*