     /**
      Creates an array of all vertices reachable from a vertex.
 
-     A *default implementation* using `vertices` and `edgeExists` is provided.
-     It works in O(V) time.
-
      - parameter vertex: The vertex whose neighbors to retrieve.
 
      - returns: An array of all vertices with edges from `vertex` to them, in no

     column was in the matrix, or `.Zero` otherwise.

     - parameter col: The column to be removed.

     - complexity: O(`nRows` * `nCols`)
    */

}

/**
 Adjacency matrices for general graphs.

 The `AdjacencyMatrix` class is only capable of keeping track of the size and
 shape of the matrix.  To use adjacency matrices as graphs, use its subclasses,
