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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 validate_polygon(obj):
 """ Make sure an input can be returned as a valid polygon. Parameters obj : shapely.geometry.Polygon, str (wkb), or (n, 2) float Object which might be a polygon Returns polygon : shapely.geometry.Polygon Valid polygon object Raises ValueError If a valid finite- area polygon isn't available """

    if isinstance(obj, Polygon):
        polygon = obj
    elif util.is_shape(obj, (-1, 2)):
        polygon = Polygon(obj)
    elif util.is_string(obj):
        polygon = load_wkb(obj)
    else:
        raise ValueError('Input not a polygon!')

    if (not polygon.is_valid or
            polygon.area < tol.zero):
        raise ValueError('Polygon is zero- area or invalid!')
    return polygon