code: public static CreateUserRequest checkRequest(
  			final FormItemList formItemList, final CreateRequest createRequest,
  			final CreateUserResponse createUserResponse) {
  		final String userId = checkUserIdentifier(formItemList,
  				createUserResponse);
  		if (userId != null) {
  			final String displayName = checkDisplayName(formItemList,
  					createUserResponse);
  			if (displayName != null) {
  				final String profilePicturePath = checkProfilePicturePath(
  						formItemList, createUserResponse);
  				return new CreateUserRequest(createRequest.getType(), userId,
  						displayName, profilePicturePath);
  			}
  		}
  
  		return null;
  	}
docs: check a create user request for validity concerning NSSP
  
  @param formItemList
  form item list extracted
  @param createRequest
  basic create request object
  @param createUserResponse
  create user response object
  @return create user request object<br>
  <b>null</b> if the create user request is invalid