docs: def authenticate(self):
          """Set BitMEX authentication information."""
          if self.apiKey:
              return
          loginResponse = self._curl_bitmex(
              api="user/login",
              postdict={'email': self.login, 'password': self.password, 'token': self.otpToken})
          self.token = loginResponse['id']
          self.session.headers.update({'access-token': self.token})