code: function isFormData(obj) {
      return Object.keys(obj).some((key) => {
          if (obj[key] instanceof stream.Stream) return true;
          if (Buffer.isBuffer(obj[key])) return true;
          return false;
      });
  }
docs: Methods
  @private
   
  Checks whether an object is multipart/form-data
  @private
  
  @param  {Object} obj - An object with form-data
  @return {Boolean}