What does the following code do$?$

new$\_$format $=$ old$\_$format.read$()$

Reads the old$\_$format variable, which contains a file, and stores it as a string in new$\_$format

Inserts the string stored in the new$\_$format variable into the file stored in the old$\_$format variable

Detects certain text patterns in old$\_$format

Prints the contents of old$\_$format