code: def contours(
          self, elevation, interval=100, field='elev', base=0
      ):
          
          return commons_contours.extract_contours(
              elevation, self.tile, interval=interval, field=field, base=base)
docs: Extract contour lines from elevation data.
  
          Parameters
          ----------
          elevation : array
              input elevation data
          interval : integer
              elevation value interval when drawing contour lines
          field : string
              output field name containing elevation value
          base : integer
              elevation base value the intervals are computed from
  
          Returns
          -------
          contours : iterable
              contours as GeoJSON-like pairs of properties and geometry