The purpose of the scope string is to allow us to have multiple
sessions of pig running and distinguish the operators. It's one of
those things that was put in before an actual requirement, so whether
it will prove useful or not remains to be seen.
As for removing it from explain, is it
The id in OperatorKey helps distinguish between multiple operators of same
type.
What I am proposing is just changing the toString() in OperatorKey to make
the explain output more readable, (we can change it back later or look at
other options, if any future requirements make printing of scope
