def convert_to_si(self):
if not self.is_data_loaded:<EOL><INDENT>self._import_data()<EOL><DEDENT>if self.is_ip is True:<EOL><INDENT>for coll in self._data:<EOL><INDENT>coll.convert_to_si()<EOL><DEDENT><DEDENT>self._is_ip = False<EOL>
Convert all Data Collections of this EPW object to SI units.

        This is useful when one needs to convert the EPW back to SI units
        from imperial units for processes like computing thermal comfort
        from EPW data.