title: DataFrame dtypes to list of dicts
body: <p>I have a very wide dataframe, and I need the dtypes of all the columns as a list of dicts:</p>
  <pre><code>[{'name': 'col1', 'type': 'STRING'},...]
  </code></pre>
  <p>I need to do that to supply this as the schema for a BigQuery table.</p>
  <p>How could that be achieved?</p>