code: def add_all(self, reference=None, atom_indices=None, ref_atom_indices=None):
          
          self.add_selection(list(range(self.topology.n_atoms)), reference=reference,
                             atom_indices=atom_indices, ref_atom_indices=ref_atom_indices)
docs: Adds all atom coordinates to the feature list.
          The coordinates are flattened as follows: [x1, y1, z1, x2, y2, z2, ...]
  
          Parameters
          ----------
          reference: mdtraj.Trajectory or None, default=None
              if given, all data is being aligned to the given reference with Trajectory.superpose
          atom_indices : array_like, or None
              The indices of the atoms to superpose. If not
              supplied, all atoms will be used.
          ref_atom_indices : array_like, or None
              Use these atoms on the reference structure. If not supplied,
              the same atom indices will be used for this trajectory and the
              reference one.