title: AttributeError: 'NoneType' object has no attribute 'label_map'
body: <p>I am trying to make an object detection model with the Tensorflow Lite model maker. Here is my code as well as the error I am getting.</p>
  <pre><code>import numpy as np
  import os
  
  from tflite_model_maker.config import ExportFormat
  from tflite_model_maker import model_spec
  from tflite_model_maker import object_detector
  
  import tensorflow as tf
  assert tf.__version__.startswith('2')
  
  tf.get_logger().setLevel('ERROR')
  from absl import logging
  logging.set_verbosity(logging.ERROR)
  
  spec = model_spec.get('efficientdet_lite0')
  
  train_data, validation_data, test_data =         
  object_detector.DataLoader.from_csv('/content/test_labels.csv')
  
  model = object_detector.create(train_data, model_spec=spec, epochs=50, batch_size=8,     
  train_whole_model=True, validation_data=validation_data)
  </code></pre>
  <p>Here is my full error</p>
  <pre><code>AttributeError                            Traceback (most recent call last)
  &lt;ipython-input-6-cd74bf318e21&gt; in &lt;module&gt;()
    1 
  ----&gt; 2 model = object_detector.create(train_data, model_spec=spec, epochs=50, batch_size=8, 
  train_whole_model=True, validation_data=validation_data)
  
  /usr/local/lib/python3.7/dist- 
     packages/tensorflow_examples/lite/model_maker/core/task/object_detector.py in create(cls, 
     train_data, model_spec, validation_data, epochs, batch_size, train_whole_model, do_train)
      281           model_spec.compat_tf_versions, compat.get_tf_behavior()))
      282 
      --&gt; 283     object_detector = cls(model_spec, train_data.label_map, train_data)
      284 
      285     if do_train:
  
  AttributeError: 'NoneType' object has no attribute 'label_map'
  </code></pre>
  <p>I am fairly confident my csv is good so I dont know why this is not working.</p>