code: def _cross_impl(values1, values2, start, end, signCheck):
      # Get both set of values.
      values1, values2 = _get_stripped(
          values1[start:end], values2[start:end], start > 0
      )
  
      # Compute differences and check sign changes.
      ret = 0
      diffs = compute_diff(values1, values2)
      diffs = filter(lambda x: x != 0, diffs)
      prevDiff = None
      for diff in diffs:
          if (
              prevDiff is not None
              and not signCheck(prevDiff)
              and signCheck(diff)
          ):
              ret += 1
          prevDiff = diff
      return ret
  
label_desc: Use image node_id 3 for calling a global function with example usage: _cross_impl(values1, values2, start, end, signCheck) and returns: ret