code: def login(self, username, password):
          
          response = self.session.post(
              os.path.join(self.identity_url, 'certlogin'),
              cert=self.cert_file,
              data=urllib.urlencode({
                  'username': username,
                  'password': password,
              }),
              headers={
                  'X-Application': self.app_key,
                  'Content-Type': 'application/x-www-form-urlencoded',
              },
              timeout=self.timeout,
          )
          utils.check_status_code(response, [httplib.OK])
          data = response.json()
          if data.get('loginStatus') != 'SUCCESS':
              raise exceptions.LoginError(response, data)
          self.session_token = data['sessionToken']
docs: Log in to Betfair. Sets `session_token` if successful.
  
          :param str username: Username
          :param str password: Password
          :raises: BetfairLoginError