Blender poses (lib) goes when i delete python generated keyframes from action

Question

I try to make rain 2 character read text, with some kind of python lipsync with text, code:

bpy.context.object.animation_data.action = bpy.data.actions['Face.Mouth.Talk.001']
path = 'D:\\input.txt'
frame = 1
    for c in str(input):    
        try:
            bpy.ops.pose.select_all(action='SELECT')
            s.frame_set(frame*5)
            if c.upper() in ('A'):
                bpy.ops.poselib.apply_pose(pose_index=1)
            elif c.upper() in ('B', 'P'):
                bpy.ops.poselib.apply_pose(pose_index=2)
            elif
...

That works, but when i manually delete the keyframes in the 'Face.Mouth.Talk.001' action, my lib pose poses lose there data, they don't apply. What i want is understand the relation between actions and poses (could not find explanation in sites, perhaps due to my poor english). Wy at first poses were there in action, not keyframed, and after being kayframed and keys deleted, they disapear ? Are poses always keyed in some hidden frames ?