code: def add_chi1_torsions(self, selstr="", deg=False, cossin=False, periodic=True):
          
          from .angles import SideChainTorsions
          f = SideChainTorsions(
              self.topology, selstr=selstr, deg=deg, cossin=cossin, periodic=periodic, which=['chi1'])
          self.__add_feature(f)
docs: 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.