title: Dataframe is coming up empty
body: <p>Below is my code to pull stock option data from a list of stock tickers. The code runs through all the tickers without error, but my dataframe (opt_df) meant to capture ALL the tickers' data ends up empty:</p>
  <pre><code>opt_df = DataFrame()
  
  for symbol in tickers:
      try:
          ticker = yf.Ticker(symbol)
          opt = ticker.option_chain('2021-07-30')
          opt_df.append(opt)
      except ValueError:
          continue
  </code></pre>