code: def get_closest_readlength(estimated_readlength):
      # type: (int) -> int
      
  
      readlengths = [36, 50, 75, 100]
      differences = [abs(r - estimated_readlength) for r in readlengths]
      min_difference = min(differences)
      index_of_min_difference = [i
                                 for i, d in enumerate(differences)
                                 if d == min_difference][0]
  
      return readlengths[index_of_min_difference]
docs: Find the predefined readlength closest to the estimated readlength.
  
      In the case of a tie, choose the shortest readlength.