code: def calculate_angles(detector, combs):
      
      angles = []
      pmt_angles = detector.pmt_angles
      for first, second in combs:
          angles.append(
              kp.math.angle_between(
                  np.array(pmt_angles[first]), np.array(pmt_angles[second])
              )
          )
      return np.array(angles)
docs: Calculates angles between PMT combinations according to positions in
      detector_file
  
      Parameters
      ----------
      detector_file: file from which to read the PMT positions (.detx)
      combs: pmt combinations
  
      Returns
      -------
      angles: numpy array of angles between all PMT combinations