title: Inserting NULL value to column of JSON type by multiple row insert query
body: <pre><code>rows = [{"id": 1, "json_value": [{"key": "value"}, {"key2": "value2"}]}, {"id": 2, "json_column": None}] 
  insert_query = table.insert().values(rows)
  connection.execute(insert_query)
  </code></pre>
  
  <p>Doing this will have "null" (String) entered to the row where id=2. Rather than the NULL type.</p>
  
  <p>Is there any way to properly do multiple row insert where value of some JSON columns is NULL?</p>