feature request, importers.importStep to return assembly if STEP file contains assembly

[shimwell]

Currently i am loading up assembiles using this class method

assembly=cq.Assembly().importStep('assembly_step1.step')

I normally load up step files using this importStep method

workplane = importers.importStep('assembly_step1.step')

I would ideally like to have a single interface that loads the step file and returns an assembly if the STEP is an assembly but returns a workplane if not. Or in other words it would be useful if the following asserts were true.

import cadquery as cq
from cadquery import importers
result = cq.Workplane().sphere(5)
assembly = cq.Assembly()
assembly.add(result)
assembly.export("assembly_step.step")
result.export("workplane_step.step")
loaded_object = importers.importStep('assembly_step1.step')
assert isinstance(loaded_object, cq.Assembly())
loaded_object = importers.importStep('workplane_step.step')
assert isinstance(loaded_object, cq.WorkPlane())

This is because I don't have a good efficient way to tell if the STEP file is an assembly or not

[adam-urbanczyk]

Actually the plan is to eventually deprecate this and add .load methods to Shape, Workplane, and Sketch.