code: def __init__(self, start, stop, npts):
      self.start = start
      self.stop = stop
      self.npts = npts
  
file_path: lmfit-py/tests/test_custom_independentvar.py
imports: import numpy
  from lmfit.lineshapes import gaussian
  from lmfit.models import Model
label_desc: Use image node_id 1 to create a new Stepper object  with example: obj = Stepper(start, stop, npts)