Let's start using our BFS algorithm to determine whether there are any direct flights between SFO and SEA:

subsetOfPaths = graph.bfs(
   fromExpr = "id = 'SEA'",
   toExpr = "id = 'SFO'",
   maxPathLength = 1)

display(subsetOfPaths)

As you can tell from the output, there are many direct flights between Seattle (SEA) and San Francisco (SFO):