code: def vol_tehrahedron(poly):
      
      a_pnt = np.array(poly[0])
      b_pnt = np.array(poly[1])
      c_pnt = np.array(poly[2])
      d_pnt = np.array(poly[3])
      return abs(np.dot(
          (a_pnt-d_pnt), np.cross((b_pnt-d_pnt), (c_pnt-d_pnt))) / 6)
docs: volume of a irregular tetrahedron