// <summary>
// Copies a group-by node
// </summary>
// <param name="op"> The Op to Copy </param>
// <param name="n"> The Node that references the Op </param>
// <returns> A copy of the original Node that references a copy of the original Op </returns>
public override Node Visit(GroupByOp op, Node n)
{
// Visit the Node's children and map their Vars
var children = ProcessChildren(n);
// Create a new GroupByOp that uses copies of the Key and Output VarSets of the original GroupByOp
var newGroupOp = m_destCmd.CreateGroupByOp(Copy(op.Keys), Copy(op.Outputs));
// Return a new Node that references the copied GroupByOp and has the copied child Nodes as its children
return(m_destCmd.CreateNode(newGroupOp, children));
}