ad--make-advised-docstring is a compiled Lisp function in `advice.el'.

(ad--make-advised-docstring FUNCTION &optional STYLE)

Construct a documentation string for the advised FUNCTION.
Concatenate the original documentation with the documentation
strings of the individual pieces of advice. Optional argument
STYLE specifies how to format the pieces of advice; it can be
`plain', or any other value which means the default formatting.

The advice documentation is shown in order of before/around/after
advice type, obeying the priority in each of these types.