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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def incrementor(start=0, step=1):
 """Returns a function that first returns the start value, and returns previous value + step on each subsequent call. """

  def fxn(_):
    """Returns the next value in the sequnce defined by [start::step)"""
    nonlocal start
    rval = start
    start += step
    return rval
  return fxn