docs: def get_atoms(self, ligands=True, pseudo_group=False, inc_alt_states=False):
          """ Flat list of all the `Atoms` in the `Assembly`.
  
          Parameters
          ----------
          ligands : bool, optional
              Include ligand `Atoms`.
          pseudo_group : bool, optional
              Include pseudo_group `Atoms`.
          inc_alt_states : bool, optional
              Include alternate sidechain conformations.
  
          Returns
          -------
          atoms : itertools.chain
              All the `Atoms` as a iterator.
          """
          atoms = itertools.chain(
              *(list(m.get_atoms(inc_alt_states=inc_alt_states))
                  for m in self.get_monomers(ligands=ligands,
                                             pseudo_group=pseudo_group)))
          return atoms