Initialize form metadata

def _init_metadata(self, **kwargs):
        """Initialize form metadata"""
        osid_objects.OsidObjectForm._init_metadata(self, **kwargs)
        self._output_score_default = self._mdata['output_score']['default_decimal_values'][0]
        self._input_score_end_range_default = self._mdata['input_score_end_range']['default_decimal_values'][0]
        self._input_score_start_range_default = self._mdata['input_score_start_range']['default_decimal_values'][0]