def https_proxy(self):
    """Set ivy to use an https proxy.

    Expects a string of the form http://<host>:<port>
    """
    if os.getenv('HTTPS_PROXY'):
      return os.getenv('HTTPS_PROXY')
    if os.getenv('https_proxy'):
      return os.getenv('https_proxy')
    return self.get_options().https_proxy