title: Tensorflow Objct detection API error: ValueError: ssd_mobilenet_v2 is not supported
body: <p>I am using the TF Object detection API. I am using TF2.4.1, python 3.6, and want to train the mobilenet_v2</p>
  <p>I downloaded the official <code>SSD MobileNet v2 320x320</code> <a href="https://github.com/tensorflow/models/blob/master/research/object_detection/g3doc/tf2_detection_zoo.md" rel="nofollow noreferrer">here</a>
  When running the training from</p>
  <pre><code>/tensorflow/model/research/object_detection/model_main_tf2.py
  </code></pre>
  <p>I get the follownig error:</p>
  <blockquote>
  <p>... File
  &quot;/home/base/anaconda3/envs/AIOD/lib/python3.6/site-packages/object_detection/builders/model_builder.py&quot;,
  line 251, in _check_feature_extractor_exists
  'Tensorflow'.format(feature_extractor_type))</p>
  </blockquote>
  <blockquote>
  <p>ValueError: ssd_mobilenet_v2 is not supported. See <code>model_builder.py</code>
  for features extractors compatible with different versions of
  Tensorflow</p>
  </blockquote>
  <p>in my pipeline.config file the fteature extractor is unchanged as:</p>
  <pre><code>feature_extractor {
    type: 'ssd_mobilenet_v2'
  ...
        }
  </code></pre>
  <p>in the <code>... /model_builder.py</code> I find that the <code>SSD_FEATURE_EXTRACTOR_CLASS_MAP</code>, which is checked in this case, includes the <code>ssd_mobilenet_v2</code> (Line 185 in model_builder).</p>
  <p>Before, I had a problem, that the <code>pipeline.config</code> file could not be found even so I gave the exact location. Copying the <code>pipeline.config</code> file to the <code>tensorflow/models/own_model_Dir</code> made that error dissapear. So maybe, I have to put the model I downloaded into a specfic folder?</p>
  <p><strong>Questions</strong></p>
  <hr />
  <p><strong>Does anyone know how to solve this?</strong></p>
  <p><strong>Do you know where I have to place the model? Do I also have to place it into the <code>tensorflow/models</code> dir?</strong></p>