Error find_book was not declared in this scope; did you mean add_book

This error message is indicating that the function 'find_book' is being called in the code, but it has not been declared or defined anywhere in the code. The message also suggests a possible alternative function called 'add_book'.

To resolve this error, you need to either declare and define the 'find_book' function or correct the function name to the intended function 'add_book' if that was the intended function to be called.