code: def get_wigner_seitz_cell(self) -> List[List[np.ndarray]]:
          
          vec1 = self._matrix[0]
          vec2 = self._matrix[1]
          vec3 = self._matrix[2]
  
          list_k_points = []
          for i, j, k in itertools.product([-1, 0, 1], [-1, 0, 1], [-1, 0, 1]):
              list_k_points.append(i * vec1 + j * vec2 + k * vec3)
          from scipy.spatial import Voronoi
  
          tess = Voronoi(list_k_points)
          to_return = []
          for r in tess.ridge_dict:
              if r[0] == 13 or r[1] == 13:
                  to_return.append([tess.vertices[i] for i in tess.ridge_dict[r]])
  
          return to_return
docs: Returns the Wigner-Seitz cell for the given lattice.
  
          Returns:
              A list of list of coordinates.
              Each element in the list is a "facet" of the boundary of the
              Wigner Seitz cell. For instance, a list of four coordinates will
              represent a square facet.