Creates a new ReturnableEvaluator on the fly that delgates to the passed in block to use with the traverse method. The block should return either true or false See api.neo4j.org/current/org/neo4j/api/core/ReturnableEvaluator.html#isReturnableNode(org.neo4j.api.core.TraversalPosition)

Examples:

  Return.when do |current_position|
    current_position.depth > 3 && current_position.previousNode[:active] == false
  end