How to run ABAQUS noGUI mdb.openStep function?

Question

I have a python script myscript.py where i read a step file into a new modeldatabase, with the following Code:

from abaqus import *
from abaqusConstants import *
backwardCompatibility.setValues(includeDeprecated=True, reportDeprecated=False)

mdb.Model("Model-1")
stepFile = r"C:\...\file.step"

step = mdb.openStep(stepFile, scaleFromFile=OFF)
Part = mdb.Model["Model-1"].PartFromGeometryFile(combine=False, dimensionality=THREE_D, geometryFile=step,
                                                 name="Part-1", type=DEFORMABLE_BODY)
...

If i run this script in the command line with abaqus cae noGUI=myscript.py i get the error message 'Mdb' object has no attribute 'openStep'

Why is this script not working with noGUI?

If i run the script with abaqus cae script=myscript.py everything runs fine.

Since my automation is a parameter study with a lot of cases i need to get the runtime down -> noGUI.