An UndirectedGraph is a DataStructure containing a vertex set ''V'' and an edge set ''E'', where each edge is an unordered pair of vertices.

Variants of this data structure:
	* Ordered pairs may be used to hold the vertices instead of unordered pairs, resulting in a DirectedGraph.
	* Weights may be associated with the edges, resulting in a WeightedUndirectedGraph.
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Definition: http://www.nist.gov/dads/HTML/undirectgraf.html
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CategoryDataStructure