title: numpy.ndarray object has no attribute 'is_all_dates'
body: <p><a href="https://i.stack.imgur.com/5l8Yl.png" rel="nofollow noreferrer">Dataframe</a>:</p>
  <p>I have a DataFrame (df) with <strong>ds</strong> and <strong>y</strong> columns for forecasting with FB Prophet. Here's the code:</p>
  <pre><code>from fbprophet import Prophet
  
  m=Prophet
  m.fit(df)
  future = m.make_future_dataframe(periods=180)
  
  forecast = m.predict(future)
  figure = m.plot(forecast)
  </code></pre>
  <p>I get the error <code>numpy.ndarray object has no attribute 'is_all_dates'</code></p>
  <p>This is quite a bizzare error as this code works with other notebooks. Any ideas? Thanks</p>