old_contents: MM = 1.
  M = 1000 * MM
  
  NS = 1.
  S = 10**9 * NS
  
  SPEED_OF_LIGHT = 299792458. * M / S
  SPEED = (2./3.) * SPEED_OF_LIGHT
  
  LENGTH = 500. * MM
  
  
new_contents: MM = 1.
  M = 1000 * MM
  
  NS = 1.
  S = 10**9 * NS
  
  SPEED_OF_LIGHT = 299792458. * M / S
  SPEED = (2./3.) * SPEED_OF_LIGHT
  
  LENGTH = 500. * MM
  
  PMT_COORDS = [(0., 0.), (LENGTH, 0.), (0., LENGTH), (LENGTH, LENGTH)]
  
  
subject: Add PMT coordinates