Pretty print the graph.  @imarks determine whether the printed graph
        represents instructions (coarse grained) for easier navigation,  or
        exact statements.

def pp(self, imarks=False):
        """
        Pretty print the graph.  @imarks determine whether the printed graph
        represents instructions (coarse grained) for easier navigation,  or
        exact statements.
        """
        for e in self.graph.edges():
            data = dict(self.graph.get_edge_data(e[0], e[1]))
            data['label'] = str(data['label']) + " ; " +  self._simproc_info(e[0]) + self._simproc_info(e[1])
            self._print_edge(e, data, imarks)