How to check if optional function parameter is set

Question

I want to append some code to the bpy.app.handlers.render_post operator. But I need to know whether the bpy.ops.render.render() operator has been called with the animation parameter (/argument?) set to True or False.

import bpy

def mRenderOutput(scene):
    print(getattr(bpy.ops.render.render, "animation"))
    #something like: if bpy.ops.render.render.animation == True: do my code

def register():
    bpy.app.handlers.render_post.append(mRenderOutput)   

def unregister():
    bpy.app.handlers.render_post.remove(mRenderOutput)

if __name__ == "__main__":
    register()

Unfortunately, this throws:

Traceback (most recent call last): File "C:\Users\morph3us\Desktop\mRenderOutput\mSaveRender001.blend\Text.004", line 4, in mRenderOutput AttributeError: 'BPyOpsSubModOp' object has no attribute 'animation'

So my question: How can I detect in an if clause inside of "mRenderOutput" whether a still image or an animation has been rendered?