title: Convert tf.keras vgg16 classifier from .pb to pbtxt for use in opencv dnn module
body: <p>I fine tuned a simple vgg16 model using tf.keras and converted it to .pb using </p>
  
  <pre><code>new_model = tf.keras.experimental.load_from_saved_model('path_to_saved_model')
  </code></pre>
  
  <p>Now I wanted to use that model in opencv dnn module so  I needed a pbtxt file , I tried converting using some scripts but failed, so i also read you can at times get aways without specifying the .pbtxt file like in east text detector, so i tried that using cv2.readfromnet(frozen.pb) approach but still it showed error and said it faced error while parsing pbtxt file</p>
  
  <p>So I tried converting to onnx format since its just a single file , but also faced error.</p>
  
  <p>Now my question is if you have successfully trained custom models and have converted the frozen graph to pbtxt then what approach do you use (Note: I'm not training a object detector  but a simple vgg16 classifier ) so the scripts in tensorflow model zoo are useless to me.</p>
  
  <p>Already spent a couple of hours in this so if you have any suggestion then would love to hear it</p>