avl-tree-mapcar is a compiled Lisp function in `avl-tree.el'.

(avl-tree-mapcar FUN TREE &optional REVERSE)

Apply FUNCTION to all elements in AVL tree TREE,
and make a list of the results.

The FUNCTION is applied and the list constructed in ascending
order, or descending order if REVERSE is non-nil.

Note that if you don't care about the order in which FUNCTION is
applied, just that the resulting list is in the correct order,

(avl-tree-mapf function 'cons tree (not reverse))

is more efficient.