<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def _construct_surface(lons, lats, upper_depth, lower_depth):
 """ Utility method that constructs and return a simple fault surface with top edge specified by `lons` and `lats` and extending vertically from `upper_depth` to `lower_depth`. The underlying mesh is built by repeating the same coordinates (`lons` and `lats`) at the two specified depth levels. """

    depths = np.array([
        np.zeros_like(lons) + upper_depth,
        np.zeros_like(lats) + lower_depth
    ])

    mesh = RectangularMesh(
        np.tile(lons, (2, 1)), np.tile(lats, (2, 1)), depths
    )
    return SimpleFaultSurface(mesh)