True if o satisfies the conditions for a path. A path shall be a map having the key :nodes, whose value shall be a sequence of vertices as defined in walkmap.polygon.

If o is a polygon, return an equivalent path. What’s different about a path is that in polygons there is an implicit edge between the first vertex and the last. In paths, there isn’t, so we need to add that edge explicitly.

If o is not a polygon, will throw an exception.