protected void extendExprGraph(LetExpression exprGraph,BlockContainer container,Set<OutputAnchor> outsideAnchors){
  connection.ifPresent(null);
}

protected void extendExprGraph ( LetExpression exprGraph , BlockContainer container , Set < OutputAnchor > outsideAnchors ) { connection . ifPresent ( null ) ; }
extends the expression graph to include all subexpression required
