GdaGraphviz Creates .dot files which can then be processed with GraphViz. An object os this class will be able to produce .dot files representing a graphical view of one or more query internals. The .dot file can be processed with the GraphViz tool (http://www.graphviz.org/). @parent_class: @dict: @Returns: @graph: @obj: @graph: @filename: @error: @Returns: