def is_derived(self):
<EOL>return bool(self._my_map['<STR_LIT>'])<EOL>
Tests if this is a calculated entry.

        return: (boolean) - ``true`` if this entry is a calculated
                entry, ``false`` otherwise. If ``true,`` then
                ``overrides_calculated_entry()`` must be ``false``.
        *compliance: mandatory -- This method must be implemented.*