Two graphs are considered identical by this function if and only if they are represented in exactly the same way in the internal R representation. This means that the two graphs must have the same list of vertices and edges, in exactly the same order, with same directedness, and the two graphs must also have identical graph, vertex and edge attributes.
Details
This is similar to identical in the base package,
but it ignores the mutable piece of igraph objects; those might be
different even if the two graphs are identical.
Attribute comparison can be turned off with the attrs parameter if
the attributes of the two graphs are allowed to be different.