For more information about general sequence and array predicates, see Sequences Arrays Vectors, and Arrays.
This function returns t if object is a string, nil otherwise. 
This function returns t if object is a string or nil. It returns nil otherwise. 
This function returns t if object is a string or a character (i.e., an integer), nil otherwise. 
    Copyright © 1990-1996, 1998-2022 Free Software Foundation, Inc. 
Licensed under the GNU GPL license.
    https://www.gnu.org/software/emacs/manual/html_node/elisp/Predicates-for-Strings.html