crm--collection-fn is a compiled Lisp function in `crm.el'.

(crm--collection-fn STRING PREDICATE FLAG)

Function used by `completing-read-multiple' to compute completion values.
The value of STRING is the string to be completed.

The value of PREDICATE is a function to filter possible matches, or
nil if none.

The value of FLAG is used to specify the type of completion operation.
A value of nil specifies `try-completion'. A value of t specifies
`all-completions'. A value of lambda specifies a test for an exact match.

For more information on STRING, PREDICATE, and FLAG, see the Elisp
Reference sections on 'Programmed Completion' and 'Basic Completion