||This class parses an inputstream or a string in
||This class parses input in DOT format, and
builds the datastructures that are passed to it.
||This class represents an edge in the graph
||This class represents a node in the Graph.
||This class displays the graph we want to visualize.
||This class lays out the vertices of a graph in a
hierarchy of vertical levels, with a number of nodes
in each level.
||This is an event which is fired by a LayoutEngine once
a LayoutEngine finishes laying out the graph, so
that the Visualizer can repaint the screen to show