title: py4j.protocol.Py4JNetworkError: Answer from Java side is empty
body: <p>This is the code I am using on Google Colab. It keeps getting stuck at the model.fit part and throws this exception. I haven't been able to find any solutions for it anywhere. The memory also seems to get very high on Colab, starting to think there's a memory leak in the spark nlp library.</p>
  <pre><code>import sparknlp
  spark = sparknlp.start()
  
  data = spark.read.csv(&quot;60days-ofdata.csv&quot;, header=True)
  
  from sparknlp.pretrained import PretrainedPipeline
  from sparknlp import Finisher
  from pyspark.ml import Pipeline
  
  finisher = Finisher().setInputCols([&quot;token&quot;, &quot;lemmas&quot;, &quot;pos&quot;])
  explain_pipeline_model = PretrainedPipeline(&quot;explain_document_ml&quot;).model
  
  pipeline = Pipeline() \
      .setStages([
          explain_pipeline_model,
          finisher
          ])
  
  model = pipeline.fit(data.select('text'))
  annotations_finished_df = model.transform(data.select('text'))
  
  remover = StopWordsRemover(inputCol=&quot;finished_lemmas&quot;, outputCol=&quot;filtered&quot;)
  filtered_df = remover.transform(text_lemmas)
  filtered_df.show()
  
  cv = CountVectorizer(inputCol=&quot;filtered&quot;, outputCol=&quot;features&quot;)
  model = cv.fit(filtered_df.select('filtered')) &lt;--------------------------------error thrown while here
  result = model.transform(filtered_df.select('filtered'))
  </code></pre>
  <p>Error:</p>
  <pre><code>INFO:py4j.java_gateway:Error while receiving.
  Traceback (most recent call last):
    File &quot;/usr/local/lib/python3.7/dist-packages/py4j/java_gateway.py&quot;, line 1207, in send_command
      raise Py4JNetworkError(&quot;Answer from Java side is empty&quot;)
  py4j.protocol.Py4JNetworkError: Answer from Java side is empty
  ERROR:root:Exception while sending command.
  Traceback (most recent call last):
    File &quot;/usr/local/lib/python3.7/dist-packages/py4j/java_gateway.py&quot;, line 1207, in send_command
      raise Py4JNetworkError(&quot;Answer from Java side is empty&quot;)
  py4j.protocol.Py4JNetworkError: Answer from Java side is empty
  
  During handling of the above exception, another exception occurred:
  
  Traceback (most recent call last):
    File &quot;/usr/local/lib/python3.7/dist-packages/py4j/java_gateway.py&quot;, line 1033, in send_command
      response = connection.send_command(command)
    File &quot;/usr/local/lib/python3.7/dist-packages/py4j/java_gateway.py&quot;, line 1212, in send_command
      &quot;Error while receiving&quot;, e, proto.ERROR_ON_RECEIVE)
  py4j.protocol.Py4JNetworkError: Error while receiving
  ---------------------------------------------------------------------------
  Py4JError                                 Traceback (most recent call last)
  &lt;ipython-input-8-0caf2f9be8f3&gt; in &lt;module&gt;()
        5 
        6 cv = CountVectorizer(inputCol=&quot;filtered&quot;, outputCol=&quot;features&quot;)
  ----&gt; 7 model = cv.fit(filtered_df.select('filtered'))
        8 result = model.transform(filtered_df.select('filtered'))
        9 result.show()
  
  5 frames
  /usr/local/lib/python3.7/dist-packages/py4j/protocol.py in get_return_value(answer, gateway_client, target_id, name)
      334             raise Py4JError(
      335                 &quot;An error occurred while calling {0}{1}{2}&quot;.
  --&gt; 336                 format(target_id, &quot;.&quot;, name))
      337     else:
      338         type = answer[1]
  
  Py4JError: An error occurred while calling o538.fit
  </code></pre>