code: def closest_ref_length(references, hyp_len):
      """
      This function finds the reference that is the closest length to the
      hypothesis. The closest reference length is referred to as *r* variable
      from the brevity penalty formula in Papineni et. al. (2002)
  
      :param references: A list of reference translations.
      :type references: list(list(str))
      :param hyp_len: The length of the hypothesis.
      :type hyp_len: int
      :return: The length of the reference that's closest to the hypothesis.
      :rtype: int
      """
      ref_lens = (len(reference) for reference in references)
      closest_ref_len = min(
          ref_lens,
          key=lambda ref_len: (abs(ref_len - hyp_len), ref_len),
      )
      return closest_ref_len
  
imports: import math
  import sys
  import warnings
  from collections import Counter
  from fractions import Fraction
  from nltk.util import ngrams
label_desc: Use image node_id 4 for calling a global function with example usage: closest_ref_length(references, hyp_len) and returns: closest_ref_len