code: def _get_contour_values(min_val, max_val, base=0, interval=100):
      
      i = base
      out = []
      if min_val < base:
          while i >= min_val:
              i -= interval
      while i <= max_val:
          if i >= min_val:
              out.append(i)
          i += interval
      return out
docs: Return a list of values between min and max within an interval.