anchor.diff:  ----
   CREATE INDEX ON :Actor(name)
   ----
  +
  +////
  +Indexes added: 1
  +////
   
   Indexes can be added at any time.
   Constraints can be added after a label is already in use, but that requires that the existing data complies with the constraints.
  
positive.code: RETURN actor;
  ----
  
  Now let's say we want to add another label for a node.
  Here's how to do that:
  
  
negative.code: CREATE CONSTRAINT ON (movie:Movie) ASSERT movie.title IS UNIQUE
  ----
  
  ////
  Constraints added: 1
  ////
  
  // console
  
  Note that adding the unique constraint will add an index on that property, so we won't do that separately.
  