BaseModel methods replacement

BaseModel.py

class BaseModelExtend(models.AbstractModel):
    _name = 'basemodel.extend'
    models.BaseModel._navigation = 'id'

    def _register_hook(self):
        @api.multi
        def _read_group_process_groupby(self, gb, query):
            split = gb.split(':')
            field_type = self._fields[split[0]].type
            gb_function = split[1] if len(split) == 2 else None
            temporal = field_type in ('date', 'datetime')
            tz_convert = field_type == 'datetime' and self._context.get('tz') in pytz.all_timezones
            qualified_field = self._inherits_join_calc(self._table, split[0], query)
            if temporal:
                display_formats = {
                    # Careful with week/year formats:
                    #  - yyyy (lower) must always be used, *except* for week+year formats
                    #  - YYYY (upper) must always be used for week+year format
                    #         e.g. 2006-01-01 is W52 2005 in some locales (de_DE),
                    #                         and W1 2006 for others
                    #
                    # Mixing both formats, e.g. 'MMM YYYY' would yield wrong results,
                    # such as 2006-01-01 being formatted as "January 2005" in some locales.
                    # Cfr: http://babel.pocoo.org/docs/dates/#date-fields
                    'hour': 'HH',  # yyyy = normal year
                    'day': 'dd MMM yyyy',  # yyyy = normal year
                    'week': "'W'w YYYY",  # w YYYY = ISO week-year
                    'month': 'MMMM yyyy',
                    'quarter': 'QQQ yyyy',
                    'year': 'yyyy',
                }
                time_intervals = {
                    'hour': dateutil.relativedelta.relativedelta(hour=1),
                    'day': dateutil.relativedelta.relativedelta(days=1),
                    'week': datetime.timedelta(days=7),
                    'month': dateutil.relativedelta.relativedelta(months=1),
                    'quarter': dateutil.relativedelta.relativedelta(months=3),
                    'year': dateutil.relativedelta.relativedelta(years=1)
                }
                if tz_convert:
                    qualified_field = "timezone('%s', timezone('UTC',%s))" % (self._context.get('tz', 'UTC'), qualified_field)
                qualified_field = "date_trunc('%s', %s)" % (gb_function or 'month', qualified_field)
            if field_type == 'boolean':
                qualified_field = "coalesce(%s,false)" % qualified_field
            return {
                'field': split[0],
                'groupby': gb,
                'type': field_type,
                'display_format': display_formats[gb_function or 'month'] if temporal else None,
                'interval': time_intervals[gb_function or 'month'] if temporal else None,
                'tz_convert': tz_convert,
                'qualified_field': qualified_field
            }
        models.BaseModel._read_group_process_groupby = _read_group_process_groupby
        return super(BaseModelExtend, self)._register_hook()