INTERFACE FOR POLYGONS
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polygon = Polygon(x1, y1, ..., xn, yn)
polygon = Polygon(p1, ..., pn)
repr(polygon)   # return string
hash(polygon)
poly1 == poly2, poly1 != poly2
polygon.move(x, y)   # return new polygon
polygon.move(point)   # return new polygon
polygon.copy()   # return polygon
polygon.orientation(test_is_simple=False)   # return -1|+1, for simple polygons
point in polygon   # return bool, using winding number
polygon.is_simple()   # return bool (slow)
polygon.is_convex(test_is_simple=False)   # return bool, for simple polygons
polygon.iterpoints()
polygon.itersegments()   # segment.pt1 < segment.pt2
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EOF
