Get the crystal system for the structure, e.g., (triclinic,
        orthorhombic, cubic, etc.).

        Returns:
            (str): Crystal system for structure or None if system cannot be detected.

def get_crystal_system(self):
        """
        Get the crystal system for the structure, e.g., (triclinic,
        orthorhombic, cubic, etc.).

        Returns:
            (str): Crystal system for structure or None if system cannot be detected.
        """
        n = self._space_group_data["number"]

        f = lambda i, j: i <= n <= j
        cs = {"triclinic": (1, 2), "monoclinic": (3, 15),
              "orthorhombic": (16, 74), "tetragonal": (75, 142),
              "trigonal": (143, 167), "hexagonal": (168, 194),
              "cubic": (195, 230)}

        crystal_sytem = None

        for k, v in cs.items():
            if f(*v):
                crystal_sytem = k
                break
        return crystal_sytem