Like GetSiblingMap(), but constructs the map starting from the vector of
incoming edge ids returned by GetInEdgeIds(). (This operation is a no-op
except unless undirected degenerate edges are present, in which case such
edges are grouped together in pairs to satisfy the requirement that every
edge must have a sibling edge.)
Like GetSiblingMap(), but constructs the map starting from the vector of incoming edge ids returned by GetInEdgeIds(). (This operation is a no-op except unless undirected degenerate edges are present, in which case such edges are grouped together in pairs to satisfy the requirement that every edge must have a sibling edge.)