void addEdge(MethodParameter in,MethodParameter out){
  Set<MethodParameter> outs=graph.get(in);
  if (outs == null) {
    outs=new HashSet<>();
    graph.put(in,outs);
  }
  outs.add(out);
}

void addEdge ( MethodParameter in , MethodParameter out ) { Set < MethodParameter > outs = graph . get ( in ) ; if ( outs == null ) { outs = new HashSet < > ( ) ; graph . put ( in , outs ) ; } outs . add ( out ) ; }
adds edge to the string passthru graph
