get-keymaps in editor:file-mixin

The keymaps returned from this method are chained to this editor<%>'s keymap.

The result of this method should not change - that is, it should return the same list of keymaps each time it is called.

• (send an-editor:file-mixin get-keymaps (list-of (instance keymap%))

  This returns a list containing the super-class's keymaps, plus the result of keymap:get-file