def METHOD_NAME(self, zindex):
    """ Return the minimum width of a layer. """
    layer_name = self.get_layer(zindex)
    min_wire_width = drc("minwidth_{0}".format(layer_name), 0, math.inf)
    min_width = self.route_track_width * drc("minwidth_{0}".format(layer_name), self.route_track_width * min_wire_width, math.inf)
    return min_width