''

def _filepath(self, layer, coord, format):

    l = layer.name()
    z = ('%d' % coord.zoom)
    e = format.lower()
    x = ('%06d' % coord.column)
    y = ('%06d' % coord.row)
    (x1, x2) = (x[:3], x[3:])
    (y1, y2) = (y[:3], y[3:])
    filepath = os.sep.join((l, z, x1, x2, y1, ((y2 + '.') + e)))
    return filepath
