code: def __make_footprint(input, size, footprint):
      "Creates a standard footprint element ala scipy.ndimage."
      if footprint is None:
          if size is None:
              raise RuntimeError("no footprint or filter size provided")
          sizes = _ni_support._normalize_sequence(size, input.ndim)
          footprint = numpy.ones(sizes, dtype=bool)
      else:
          footprint = numpy.asarray(footprint, dtype=bool)
      return footprint
  
imports: import numpy
  from scipy.ndimage import _ni_support
  from ..io import header
label_desc: Use image node_id 4 for calling a global function with example usage: __make_footprint(input, size, footprint) and returns: footprint