title: Json Serialize Class with Pandas Dataframe Property: TypeError: Object of type 'DataFrame' is not JSON serializable
body: <p>HI I have a class with a pandas dataframe property. How do I encode to json so that the pandas dataframe property gets properly serialized too ?</p>
  <pre><code>class MachineObject(dict):
      def __init__(self, *args, **kwargs):       
          self._MachineName = ''
          self._propsDataFrame = None # Pandas dataframe
     
  </code></pre>
  <p>I am serializing like so:</p>
  <pre><code>print(json.dumps(machine_objects[0].__dict__))
  </code></pre>
  <p>but that is giving me errors:</p>
  <pre><code>TypeError: Object of type 'DataFrame' is not JSON serializable
  </code></pre>
  <p>Thanks</p>