docstr: target: test compact multi collections with merge
  method: create 50 collections, add entities into them and compact in turn
  expected: No exception
docstr_tok: ["target",":","test","compact","multi","collections","with","merge","method",":","create","50","collections",",","add","entities","into","them","and","compact","in","turn","expected",":","No","exception"]
code: def test_compact_multi_collections(self):
      """
      target: test compact multi collections with merge
      method: create 50 collections, add entities into them and compact in turn
      expected: No exception
      """
      pass
  
imports: import threading
  from time import time, sleep
  import pytest
  from pymilvus.grpc_gen.common_pb2 import SegmentState
  from pymilvus.exceptions import MilvusException
  from base.client_base import TestcaseBase
  from common import common_func
  from common import common_type
  from common.common_type import CaseLabel, CheckTasks
  from utils.util_log import test_log
label_desc: Use image node_id 17 for calling the TestCompactionOperation obj's underlying member method code with example usage: obj.test_compact_multi_collections() without return types