    graph.getSubgraph(cells [, opt])

Return an array of cells that result from finding elements/links that are connected to any of the cells in the `cells` array. This function loops over `cells` and if the current cell is a link, it collects its source/target elements; if it is an element, it collects its incoming and outgoing links if both the link ends (source/target) are in the `cells` array. For example, for a single element, the result is that very same element. For two elements connected with a link: `A --- L ---> B`, the result of `getSubgraph([A, B])` is `[A, L, B]` and the result of `getSubgraph([L])` is also `[A, L, B]`.
If `opt.deep` is `true` take into account all the embedded cells too when finding neighboring links/elements.