def add_chi1_torsions(self, selstr="", deg=False, cossin=False, periodic=True):
        """
        Adds all chi1 angles or the ones specified in :obj:`selstr` to the feature list.

        Parameters
        ----------

        selstr : str, optional, default = ""
            selection string specifying the atom selection used to specify a specific set of backbone angles
            If "" (default), all chi1 angles found in the topology will be computed
        deg : bool, optional, default = False
            If False (default), angles will be computed in radians.
            If True, angles will be computed in degrees.
        cossin : bool, optional, default = False
            If True, each angle will be returned as a pair of (sin(x), cos(x)).
            This is useful, if you calculate the mean (e.g TICA/PCA, clustering)
            in that space.
        periodic : bool, optional, default = True
            If `periodic` is True and the trajectory contains unitcell
            information, we will treat dihedrals that cross periodic images
            using the minimum image convention.
        """
        from .angles import SideChainTorsions
        f = SideChainTorsions(
            self.topology, selstr=selstr, deg=deg, cossin=cossin, periodic=periodic, which=['chi1'])
        self.__add_feature(f)
Adds all chi1 angles or the ones specified in :obj:`selstr` to the feature list.

        Parameters
        ----------

        selstr : str, optional, default = ""
            selection string specifying the atom selection used to specify a specific set of backbone angles
            If "" (default), all chi1 angles found in the topology will be computed
        deg : bool, optional, default = False
            If False (default), angles will be computed in radians.
            If True, angles will be computed in degrees.
        cossin : bool, optional, default = False
            If True, each angle will be returned as a pair of (sin(x), cos(x)).
            This is useful, if you calculate the mean (e.g TICA/PCA, clustering)
            in that space.
        periodic : bool, optional, default = True
            If `periodic` is True and the trajectory contains unitcell
            information, we will treat dihedrals that cross periodic images
            using the minimum image convention.