A callable with prototype that is one of RangeType GetKeyEdges(const KeyType& Key); /** Convert an array of Keys and a function that returns the directed edges from each Key into the Normalized Graph Form. Normalized Graph Form is an implicit set of vertices identified as integers from 0 to N - 1, and an array of arrayviews of edges from each vertex. The Normalized Graph form has two structures: The buffer which contains the memory storage for the graph and the graph itself which is the array of arrayviews of edges. The length of the array in the graph defines the number of vertices.