code: def _cut_time(gammas):
      
  
      for i in range(len(gammas) - 1):
  
          if not ((gammas[i + 1] > 0.0) & (gammas[i + 1] < gammas[i])):
              return i
  
      return i
docs: Support function for iat().
      Find cutting time, when gammas become negative.