Generator of features.

        If a gffutils.FeatureDB is attached, returns a pybedtools.Interval for
        every feature in the dataframe's index.

        Parameters
        ----------
        ignore_unknown : bool
            If True, silently ignores features that are not found in the db.

def features(self, ignore_unknown=False):
        """
        Generator of features.

        If a gffutils.FeatureDB is attached, returns a pybedtools.Interval for
        every feature in the dataframe's index.

        Parameters
        ----------
        ignore_unknown : bool
            If True, silently ignores features that are not found in the db.
        """
        if not self.db:
            raise ValueError("Please attach a gffutils.FeatureDB")
        for i in self.data.index:
            try:
                yield gffutils.helpers.asinterval(self.db[i])
            except gffutils.FeatureNotFoundError:
                if ignore_unknown:
                    continue
                else:
                    raise gffutils.FeatureNotFoundError('%s not found' % i)