code: public function post($endpoint, $data, $headers = [])
      {
          $request = new Request('POST', $endpoint, $headers, $data);
  
          $response = $this->guzzle->send($request);
  
          return $this->handle($response);
      }
docs: Create a new POST reuest.
  
  @param string       $endpoint The sub endpoint
  @param string|array $data     The data to be submited
  @param array        $headers  Request headers
  
  @return array