How to use the pydal.helpers.serializers.serializers.json function in pydal

def represent(self, obj, fieldtype, tablename=None):
        if isinstance(obj, ndb.Key):
            return obj
        elif fieldtype == 'id' and tablename:
            if isinstance(obj, list):
                return [self.represent(item,fieldtype,tablename) for item in obj]
            elif obj is None:
                return None
            else:
                return ndb.Key(tablename, long(obj))
        elif fieldtype == "json":
            return serializers.json(obj)
        elif isinstance(obj, (Expression, Field)):
            raise SyntaxError("non supported on GAE")
        elif isinstance(fieldtype, gae.Property):
            return obj
        elif fieldtype.startswith('list:') and not isinstance(obj, list):
            if fieldtype=='list:string': return str(obj)
            else: return long(obj)
        else:
            obj = NoSQLAdapter.represent(self, obj, fieldtype)
            return obj

def represent(self, obj, fieldtype):
        value = NoSQLAdapter.represent(self, obj, fieldtype)
        if fieldtype == 'id':
            return repr(str(long(value)))
        elif fieldtype in ('date', 'time', 'datetime', 'boolean'):
            return serializers.json(value)
        return repr(not isinstance(value, unicode) and value
                    or value and value.encode('utf8'))

def _json(self, value):
        return serializers.json(value)

):
        """
        serializes the row to a JSON object
        kwargs are passed to .as_dict method
        only "object" mode supported

        `serialize = False` used by Rows.as_json

        TODO: return array mode with query column order

        mode and colnames are not implemented
        """

        item = self.as_dict(**kwargs)
        if serialize:
            return serializers.json(item)
        else:
            return item

def _datetime(self, value):
        return serializers.json(value)

def _json(self, value):
        return serializers.json(value)