title: Python requests can't send multiple headers with same key
body: <p>I'm trying to send a GET request to a server with two headers which have the same name, but different values:</p>
  <pre><code>url = 'whatever'
  headers = {'X-Attribute': 'A', 'X-Attribute': 'B'}
  requests.get(url, headers = headers)
  </code></pre>
  <p>This obviously doesn't work, since the headers dictionary can't contain two keys <code>X-Attribute</code>.</p>
  <p>Is there anything I can do, i.e. can I pass headers as something other than a dictionary?  The requirement to send requests in this manner is a feature of the server, and I can't change it.</p>