docstr: Merge two clusters together
docstr_tok: ["Merge","two","clusters","together"]
code: def _merge_coreference_clusters(self, ant_flat_idx, mention_flat_idx):
      """
      Merge two clusters together
      """
      doc_idx, ant_idx = self.flat_m_idx[ant_flat_idx]
      doc_idx2, mention_idx = self.flat_m_idx[mention_flat_idx]
      assert doc_idx2 == doc_idx
      if (
          self.mention_to_cluster[doc_idx][ant_idx]
          == self.mention_to_cluster[doc_idx][mention_idx]
      ):
          return
      remove_id = self.mention_to_cluster[doc_idx][ant_idx]
      keep_id = self.mention_to_cluster[doc_idx][mention_idx]
      for idx in self.clusters[doc_idx][remove_id]:
          self.mention_to_cluster[doc_idx][idx] = keep_id
          self.clusters[doc_idx][keep_id].append(idx)
      del self.clusters[doc_idx][remove_id]
  
imports: import os
  import subprocess
  import io
  import pickle
  import torch
  from torch.utils.data import DataLoader
  from neuralcoref.train.conllparser import FEATURES_NAMES
  from neuralcoref.train.dataset import NCBatchSampler, padder_collate
  from neuralcoref.train.compat import unicode_
label_desc: Use image node_id 4 for calling the ConllEvaluator obj's underlying member method code with example usage: obj._merge_coreference_clusters(ant_flat_idx, mention_flat_idx) without return types