code: public String delete_user(Map<String, String> data) {
          String id = data.get("email");
          return delete("user/" + id, EMPTY_STRING);
      }
docs: /*
  Unlink existing user from all lists.
  @param {Object} data contains json objects as a key value pair from HashMap.
  @options data {String} email: Email address of the already existing user in the SendinBlue contacts to be unlinked from all lists [Mandatory]