The function tried to rearrange properties but that lead to problems with duplication or deleted properties. Implemented the logic that that function did inside the get_property_list both for tool scripts and non-tool scripts.
Mapping and other "abstract base classes" were moved after python 3.3 from collections to collections.abc
Python 3.3 is long gone and a newer version of python won't support this code.
When emitting stops CPUParticles3D::_set_redraw(bool p_redraw) will set that value to 0 so when you change the amount after that it will actually not update correclty.
This fixes an issue where if it was not emitting when the scene loaded and it start after that the amount is not reflected correclty. This also happened when you checked out the box for emitting in the editor, changed the value of amount and then checked on the box for emitting. With this change if it is emitting during the change it does interrupt the previous particles when you change. The amount and the emit starts from beginning but that is to be expected on an amount of particles change.
Hristo Stamenov