+ """Returns True if filename was written today.
+
+ >>> import os
+ >>> filename = f'/tmp/testing_persistent_py_{os.getpid()}'
+ >>> os.system(f'touch {filename}')
+ 0
+ >>> was_file_written_today(filename)
+ True
+ >>> os.system(f'touch -d 1974-04-15T01:02:03.99 {filename}')
+ 0
+ >>> was_file_written_today(filename)
+ False
+ >>> os.system(f'/bin/rm -f {filename}')
+ 0
+ >>> was_file_written_today(filename)
+ False
+ """