public Direction getDirection() {
        return this.direction;
    }
Handles the logic of traversing to adjacent vertices or edges given a direction and edge labels for steps like,
{@code out}, {@code in}, {@code both}, {@code outE}, {@code inE}, and {@code bothE}.

@author Marko A. Rodriguez (http://markorodriguez.com)
gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/process/traversal/step/map/VertexStep.java