user: What is Using the Pose Library and how is it used in Blender Python scripting?

assistant: The pose library can be used to pose one or more characters.
The current bone selection will be used to determine which bones are modified.
When editing multiple armatures at once, a matching [slot](../../../actions.xhtml#animation-actions-slots)
of the pose asset is determined for each armature.
It is possible to either fully apply a pose or blend it into
the character’s current pose interactively.
How exactly these operations work depends on where you use them.
This section will explain the use from both the Asset Browser and the 3D Viewport.

### Use from the Asset Browser

The pose library can be used directly from the Asset Browser.
The **Pose Library panels will appear** when the active object is an armature
and in Pose Mode. The [catalog system](../../../../files/asset_libraries/catalogs.xhtml)
and the filter bar at the top can be used to search for specific poses.

The following operators can be accessed by `RMB` on a pose:

Apply Pose
:   Applies the pose to the character. If there are any bones selected,
    the pose will be applied only to those bones. This makes it possible to
    create a “finger guns” pose by applying a fist pose to the hand,
    and then an “open hand” pose for only the index finger and thumb.
    Double-clicking a pose will also apply it.

Apply Pose Flipped
:   Will mirror the pose from left to right and vice versa. This makes it
    possible, for example, to apply a left-hand pose to the right hand, reducing
    the number of poses you have to put into the library. This can of course also
    be applied for asymmetrical facial expressions that depend on the camera
    angle. While blending (see below), keep `Ctrl` pressed to blend the flipped pose.

Blend Pose
:   Allows you to gradually blend a pose from the library into the character’s pose.
    Click the button, then move the mouse left/right to determine the desired blend.
    A pose asset can be “subtracted” while blending. Drag to the right to blend as usual, drag to the left to subtract
    the pose. While blending, you can use `Tab` to toggle between the original and the blended pose.
    As usual in Blender, `LMB` or press `Return` to confirm; `RMB` or press `Esc` to cancel the
    operator. Blending can also exaggerate a pose, by pressing `E` (for Extrapolate) and applying a pose for more
    than 100%.

Select/Deselect Pose Bones
:   Select or deselect the bones that are used in the pose. This can be used to create a selection set,
    or simply show what was part of the pose and what wasn’t.

### Use from 3D Viewport

[image reference removed]

The pose library in use from the Asset Shelf.

In the 3D viewport, poses can be quickly applied from the [Asset Shelf](../../../../interface/window_system/regions.xhtml#ui-region-asset-shelf).
Contrary to the Asset Browser, the shelf allows you to apply poses quicker.

**Click on a pose to apply it.** A single click is enough.
You can also select and apply a pose via the cursor keys.
This allows for fast exploration of the poses,
to directly see the result on the active character.

**Drag the pose thumbnail left to right to blend it** into the character’s current pose.
Just release the mouse button to confirm.