text: Title: AttributeError: 'Doc2VecTrainables' object has no attribute 'vectors_lockf'
  Body: Python version 3.7.5
  gensim version 3.6.0
  apache-beam[gcp] 2.20.0 
  tensorflow==1.14
  
  #### Problem description
  Trying to create tf records using gensim Doc2Vec. 
  Expected result is to create tf records with the given parameters. 
  
  In Directrunner
  
  tf record creation is happening when used with gensim 3.6.0 
  but AttributeError is raised when ran with 3.8.0 version of gensim (AttributeError: 'Doc2VecTrainables' object has no attribute 'vectors_lockf')
  
  While running a dataflow job even with gensim 3.6.0 
  Attribute error is raised
  
  #### Steps/code/corpus to reproduce
  
  pretrained_emb = 'glove.6B.100d.txt'
          vector_size = 300
          window_size = 15
          min_count = 1
          sampling_threshold = 1e-5
          negative_size = 5
          train_epoch = 100
          dm = 0 #0 = dbow; 1 = dmpv
          worker_count = 1 #number of parallel processes
          print('max_seq_len which is being passed above Doc2Vec', self.max_seq_len)
          self.model = g.Doc2Vec(documents=None,size=vector_size,
                                 window=window_size, min_count=min_count,
                                 sample=sampling_threshold,
                                 workers=worker_count, hs=0,
                                 dm=dm, negative=negative_size,
                                 dbow_words=1, dm_concat=1,
                                 pretrained_emb=pretrained_emb,
                                 iter=100)
          print("Loaded Model")
    plot class type is 'string'
      embedding_vector = self.model.infer_vector([plot])
  
   It is raising an attribute error when ran in dataflow runner. In Directrunner issue is raised when gensim version is 3.8.0
  
  Error log:
  I have pasted the entire error log.
  textPayload: "Error message from worker: Traceback (most recent call last):
    File "apache_beam/runners/common.py", line 950, in apache_beam.runners.common.DoFnRunner.process
    File "apache_beam/runners/common.py", line 547, in apache_beam.runners.common.SimpleInvoker.invoke_process
    File "apache_beam/runners/common.py", line 1078, in apache_beam.runners.common._OutputProcessor.process_outputs
    File "tfrecord_util/csv2tfrecord_train_valid.py", line 310, in process
      x = self.preprocess(x)
    File "tfrecord_util/csv2tfrecord_train_valid.py", line 233, in preprocess
      embedding_vector = self._embedding(plot)
    File "tfrecord_util/csv2tfrecord_train_valid.py", line 300, in _embedding
      embedding_vector = self.model.infer_vector([plot])
    File "/usr/local/lib/python3.7/site-packages/gensim/models/doc2vec.py", line 915, in infer_vector
      learn_words=False, learn_hidden=False, doctag_vectors=doctag_vectors, doctag_locks=doctag_locks
    File "gensim/models/doc2vec_inner.pyx", line 332, in gensim.models.doc2vec_inner.train_document_dbow
    File "gensim/models/doc2vec_inner.pyx", line 254, in gensim.models.doc2vec_inner.init_d2v_config
  AttributeError: 'Doc2VecTrainables' object has no attribute 'vectors_lockf'
  
  
  I hope you understand the issue from the above details. Please let me know if you still need any additional information.
  During handling of the above exception, another exception occurred:
  
  Traceback (most recent call last):
    File "/usr/local/lib/python3.7/site-packages/dataflow_worker/batchworker.py", line 647, in do_work
      work_executor.execute()
    File "/usr/local/lib/python3.7/site-packages/dataflow_worker/executor.py", line 176, in execute
      op.start()
    File "dataflow_worker/native_operations.py", line 38, in dataflow_worker.native_operations.NativeReadOperation.start
    File "dataflow_worker/native_operations.py", line 39, in dataflow_worker.native_operations.NativeReadOperation.start
    File "dataflow_worker/native_operations.py", line 44, in dataflow_worker.native_operations.NativeReadOperation.start
    File "dataflow_worker/native_operations.py", line 54, in dataflow_worker.native_operations.NativeReadOperation.start
    File "apache_beam/runners/worker/operations.py", line 329, in apache_beam.runners.worker.operations.Operation.output
    File "apache_beam/runners/worker/operations.py", line 192, in apache_beam.runners.worker.operations.SingletonConsumerSet.receive
    File "apache_beam/runners/worker/operations.py", line 682, in apache_beam.runners.worker.operations.DoOperation.process
    File "apache_beam/runners/worker/operations.py", line 683, in apache_beam.runners.worker.operations.DoOperation.process
    File "apache_beam/runners/common.py", line 952, in apache_beam.runners.common.DoFnRunner.process
    File "apache_beam/runners/common.py", line 1013, in apache_beam.runners.common.DoFnRunner._reraise_augmented
    File "apache_beam/runners/common.py", line 950, in apache_beam.runners.common.DoFnRunner.process
    File "apache_beam/runners/common.py", line 547, in apache_beam.runners.common.SimpleInvoker.invoke_process
    File "apache_beam/runners/common.py", line 1105, in apache_beam.runners.common._OutputProcessor.process_outputs
    File "apache_beam/runners/worker/operations.py", line 192, in apache_beam.runners.worker.operations.SingletonConsumerSet.receive
    File "apache_beam/runners/worker/operations.py", line 682, in apache_beam.runners.worker.operations.DoOperation.process
    File "apache_beam/runners/worker/operations.py", line 683, in apache_beam.runners.worker.operations.DoOperation.process
    File "apache_beam/runners/common.py", line 952, in apache_beam.runners.common.DoFnRunner.process
    File "apache_beam/runners/common.py", line 1028, in apache_beam.runners.common.DoFnRunner._reraise_augmented
    File "/usr/local/lib/python3.7/site-packages/future/utils/__init__.py", line 421, in raise_with_traceback
      raise exc.with_traceback(traceback)
    File "apache_beam/runners/common.py", line 950, in apache_beam.runners.common.DoFnRunner.process
    File "apache_beam/runners/common.py", line 547, in apache_beam.runners.common.SimpleInvoker.invoke_process
    File "apache_beam/runners/common.py", line 1078, in apache_beam.runners.common._OutputProcessor.process_outputs
    File "tfrecord_util/csv2tfrecord_train_valid.py", line 310, in process
      x = self.preprocess(x)
    File "tfrecord_util/csv2tfrecord_train_valid.py", line 233, in preprocess
      embedding_vector = self._embedding(plot)
    File "tfrecord_util/csv2tfrecord_train_valid.py", line 300, in _embedding
      embedding_vector = self.model.infer_vector([plot])
    File "/usr/local/lib/python3.7/site-packages/gensim/models/doc2vec.py", line 915, in infer_vector
      learn_words=False, learn_hidden=False, doctag_vectors=doctag_vectors, doctag_locks=doctag_locks
    File "gensim/models/doc2vec_inner.pyx", line 332, in gensim.models.doc2vec_inner.train_document_dbow
    File "gensim/models/doc2vec_inner.pyx", line 254, in gensim.models.doc2vec_inner.init_d2v_config
  AttributeError: 'Doc2VecTrainables' object has no attribute 'vectors_lockf' [while running 'PreprocessData']
  ```
  