docstr: target: test compact an empty collection
  method: compact an empty collection
  expected: No exception
docstr_tok: ["target",":","test","compact","an","empty","collection","method",":","compact","an","empty","collection","expected",":","No","exception"]
code: def test_compact_empty_collection(self):
      """
      target: test compact an empty collection
      method: compact an empty collection
      expected: No exception
      """
      # init collection and empty
      collection_w = self.init_collection_wrap(
          name=cf.gen_unique_str(prefix)
      )
  
      # compact
      collection_w.compact()
      c_plans, _ = collection_w.get_compaction_plans()
      assert len(c_plans.plans) == 0
  
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 5 for calling the TestCompactionParams obj's underlying member method code with example usage: obj.test_compact_empty_collection() without return types