INTERFACE FOR TRIANGLECOLLECTION
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tc = TriangleCollection()
str(tc)   # return string
len(tc)
tc.insert(triangle)
tc.remove(triangle)
tc.search(point)   # return a list of triangles
tc.itertriangles()
triangle in tc   # return bool
tc.to_graph()   # return a graph with points and segments
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EOF
