anchor.diff:  }
   ----
   
  -
   The traversal is redefined by simply taking a chain of `has()`-steps after `g.V()` (`TinkerGraphStep`) and providing them to `TinkerGraphStep`. Then its up to TinkerGraphStep to determine if an appropriate index exists. In the code below, review the `vertices()` method and note how if an index exists, for a particular `HasContainer`, then that index is first queried before the remaining `HasContainer` filters are serially applied.
   
   [gremlin-groovy,modern]
  
positive.code: * Vertex removed
  * Edge removed
  
  To start processing events from a `Traversal` first implement the `MutationListener` interface. An example of this implementation is the `ConsoleMutationListener` which writes output to the console for each event.
  
  
  CAUTION: `EventStrategy` is not meant for usage in tracking global mutations across separate processes.  In other words, an mutation in what JVM process is not raised as an event in a different JVM process.  In addition, events are not raised when mutations occur as part of side-effect steps (i.e. a lambda).
  
  Domain Specific Languages
  -------------------------
  
negative.code: t.toString()
  ----
  
  TinkerPop has a number of type-3 strategies distributed as part of its core library.  These strategies add generalized features to a traversal that are typically useful to end-users.  The following sections detail these strategies:
  
  EventStrategy
  =============
  