EDIT: pointed out in a comment: my code needed some error handling and I didn't demonstrate how to use an override with arguments.


Here is an example of how to use an override to allow you to invoke `apply_pose_asset`:

``` python
win = bpy.context.window
scr = win.screen
assets = [area for area in scr.areas if area.type == 'FILE_BROWSER']
if len(assets):
    region = [region for region in assets[0].regions if region.type == 'TOOLS']
    if len(region):
        override = {
            'window': win,
            'screen': scr,
            'area'  : assets[0],
            'region': region[0],
            'scene' : bpy.context.scene,
        }
        bpy.ops.poselib.apply_pose_asset(override, pose_index=- 1)
    else:
        print("Current Pose Library does not have a tools menu open.")
else:
    print("There is no Pose LIbrary open.")
```

The override is inserted into the function call as the first argument, all other arguments remaining the same.

The override argument takes the form of a Python dictionary.  Each entry represents one piece of context to override.  The above example shows the complete override for the command.  Note that the area type is `FILE_BROWSER`.  That is the area type of the editor window that the command expects to run in. 

Note:  The command itself uses the first valid entry in the catalog if none are selected, or the active entry if one is selected.