<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def feature_path(self, gff_path):
 """Load a GFF file with information on a single sequence and store features in the ``features`` attribute Args: gff_path: Path to GFF file. """

        if not gff_path:
            self.feature_dir = None
            self.feature_file = None

        else:
            if not op.exists(gff_path):
                raise OSError('{}: file does not exist!'.format(gff_path))

            if not op.dirname(gff_path):
                self.feature_dir = '.'
            else:
                self.feature_dir = op.dirname(gff_path)
            self.feature_file = op.basename(gff_path)