bpy: Delete custom properties that aren't API defined

Question

I have a addon for Blender where I'm using custom properties and I would like to delete any custom property that isn't API defined.

In my project I have an enumerator that acts like a dropdown menu to choose between different property groups(where the user can set multiple properties), with an on Change function that resets properties.

I need to do this in a dynamical ways and properties have other name and values. Is there any way to just access API defined properties or manually added properties? That would be enough.

I found out that if have a property that isn't API defined I get the following error: Error message Here are my properties: Custom Properties API defined + manually added one

This is my function:

def fun_clear_none_selected():
    # Getting props from selected object
    get_array_object = bpy.context.object.keys()
    properties = []

    # Filling data from get_array_object to properties to be able to access it
    for item in get_array_object:
        properties.append(item)

    # Permanent property
    properties.remove('toolTipTextKey')

    # Resetting unused properties
    for name in properties:
        bpy.context.object.property_unset(name)