code: public JSONAPIDocument<User> fetchUser(Collection<User.UserField> optionalFields) throws IOException {
      URIBuilder pathBuilder = new URIBuilder()
                      .setPath("current_user")
                      .addParameter("include", "pledges");
      if (optionalFields != null) {
        Set<User.UserField> optionalAndDefaultFields = new HashSet<>(optionalFields);
        optionalAndDefaultFields.addAll(User.UserField.getDefaultFields());
        addFieldsParam(pathBuilder, User.class, optionalAndDefaultFields);
      }
  
      return converter.readDocument(
        getDataStream(pathBuilder.toString()),
        User.class
      );
    }
docs: Get the user object of the creator
  
  @param optionalFields A list of optional fields to request, or null.  See {@link User.UserField}
  @return the current user
  @throws IOException Thrown when the GET request failed