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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def area_of_polygon(polygon):
 """ Returns the area of an OpenQuake polygon in square kilometres """

    lon0 = np.mean(polygon.lons)
    lat0 = np.mean(polygon.lats)
    # Transform to lamber equal area projection
    x, y = lonlat_to_laea(polygon.lons, polygon.lats, lon0, lat0)
    # Build shapely polygons
    poly = geometry.Polygon(zip(x, y))
    return poly.area