docs: def _merge_command(run, full_result, results):
      """Merge a group of results from write commands into the full result.
      """
      for offset, result in results:
  
          affected = result.get("n", 0)
  
          if run.op_type == _INSERT:
              full_result["nInserted"] += affected
  
          elif run.op_type == _DELETE:
              full_result["nRemoved"] += affected
  
          elif run.op_type == _UPDATE:
              upserted = result.get("upserted")
              if upserted:
                  if isinstance(upserted, list):
                      n_upserted = len(upserted)
                      for doc in upserted:
                          doc["index"] = run.index(doc["index"] + offset)
                      full_result["upserted"].extend(upserted)
                  else:
                      n_upserted = 1
                      index = run.index(offset)
                      doc = {_UINDEX: index, _UID: upserted}
                      full_result["upserted"].append(doc)
                  full_result["nUpserted"] += n_upserted
                  full_result["nMatched"] += (affected - n_upserted)
              else:
                  full_result["nMatched"] += affected
              n_modified = result.get("nModified")
              # SERVER-13001 - in a mixed sharded cluster a call to
              # update could return nModified (>= 2.6) or not (<= 2.4).
              # If any call does not return nModified we can't report
              # a valid final count so omit the field completely.
              if n_modified is not None and "nModified" in full_result:
                  full_result["nModified"] += n_modified
              else:
                  full_result.pop("nModified", None)
  
          write_errors = result.get("writeErrors")
          if write_errors:
              for doc in write_errors:
                  # Leave the server response intact for APM.
                  replacement = doc.copy()
                  idx = doc["index"] + offset
                  replacement["index"] = run.index(idx)
                  # Add the failed operation to the error document.
                  replacement[_UOP] = run.ops[idx]
                  full_result["writeErrors"].append(replacement)
  
          wc_error = result.get("writeConcernError")
          if wc_error:
              full_result["writeConcernErrors"].append(wc_error)