function that takes a command and a mode-map returning the bound string

Question

Is there a command ie: get-bounded-string that is available that performs this?

(defun no-op () nil)

(define-key dired-mode-map (kbd  "C-c C-7") 'no-op)

then

(get-bound-string dired-mode-map 'no-op)
=> "C-c C-7"

Answer 1

Emacs has a substitute-command-keys function, which takes a format string and substitutes occurrences of specific escape substrings according to their type. Specifically, it replaces \\[<command>] with the keybinding for <command> in the context of the current keymap.

What you can do is run the function in the context of a temporary buffer with desired keymap set. It might look something like this:

(with-temp-buffer
  (use-local-map dired-mode-map)
  (substitute-command-keys "\\[no-op]"))

You could, of course, wrap the above in a function definition.

Answer 2

You already accepted an answer as correct, but I interpreted your question differently, as wanting Elisp code that tells you what key(s) a given command is bound to in a given mode.

If you're interested in that, where-is-internal will do it for you.

For example, to find out what keys command dired-mark is bound to in Dired mode, use this:

(where-is-internal 'dired-mark dired-mode-map)

See the Elisp manual, node Scanning Keymaps.

Interactively, you have command where-is, bound to C-h w. That tells you which keys a command is bound to in the current buffer (mode).