code: def merge_score(group1, group2, special_tokens):
      """Compute the score of merging two token groups.
  
      special_tokens: tokens (such as separator tokens) that should be grouped last
      """
      score = 0
      # ensures special tokens are combined last, so 1st subtree is 1st sentence and 2nd subtree is 2nd sentence
      if len(special_tokens) > 0:
          if (
              group1[-1].s in special_tokens
              and group2[0].s in special_tokens
          ):
              score -= (
                  math.inf
              )  # subtracting infinity to create lowest score and ensure combining these groups last
  
      # merge broken-up parts of words first
      if group2[0].s.startswith("##"):
          score += 20
  
      # merge apostrophe endings next
      if group2[0].s == "'" and (
          len(group2) == 1
          or (len(group2) == 2 and group2[1].s in ["t", "s"])
      ):
          score += 15
      if group1[-1].s == "'" and group2[0].s in ["t", "s"]:
          score += 15
  
      start_ctrl = group1[0].s.startswith("[") and group1[0].s.endswith(
          "]"
      )
      end_ctrl = group2[-1].s.startswith("[") and group2[-1].s.endswith(
          "]"
      )
  
      if (start_ctrl and not end_ctrl) or (end_ctrl and not start_ctrl):
          score -= 1000
      if group2[0].s in openers and not group2[0].balanced:
          score -= 100
      if group1[-1].s in closers and not group1[-1].balanced:
          score -= 100
  
      # attach surrounding an openers and closers a bit later
      if group1[0].s in openers and group2[-1] not in closers:
          score -= 2
  
      # reach across connectors later
      if group1[-1].s in connectors or group2[0].s in connectors:
          score -= 2
  
      # reach across commas later
      if group1[-1].s == ",":
          score -= 10
      if group2[0].s == ",":
          if len(group2) > 1:  # reach across
              score -= 10
          else:
              score -= 1
  
      # reach across sentence endings later
      if group1[-1].s in [".", "?", "!"]:
          score -= 20
      if group2[0].s in [".", "?", "!"]:
          if len(group2) > 1:  # reach across
              score -= 20
          else:
              score -= 1
  
      score -= len(group1) + len(group2)
      # print(group1, group2, score)
      return score
  
imports: import math
  import re
  import numpy
  from .._serializable import Deserializer, Serializer
  from ..utils import safe_isinstance
  from ..utils.transformers import SENTENCEPIECE_TOKENIZERS, getattr_silent, parse_prefix_suffix_for_tokenizer
  from ._masker import Masker
label_desc: Use image node_id 2 for calling a global function with example usage: merge_score(group1, group2, special_tokens) and returns: score