Returns a single record for the RecordCollection, ensuring that it
        is the only record, or returns `default`. If `default` is an instance
        or subclass of Exception, then raise it instead of returning it.

def one(self, default=None, as_dict=False, as_ordereddict=False):
        """Returns a single record for the RecordCollection, ensuring that it
        is the only record, or returns `default`. If `default` is an instance
        or subclass of Exception, then raise it instead of returning it."""

        # Ensure that we don't have more than one row.
        try:
            self[1]
        except IndexError:
            return self.first(default=default, as_dict=as_dict, as_ordereddict=as_ordereddict)
        else:
            raise ValueError('RecordCollection contained more than one row. '
                             'Expects only one row when using '
                             'RecordCollection.one')