public default void addStart(final Traverser.Admin<S> start) {
            if (!this.isLocked()) this.applyStrategies();
            this.getStartStep().addStart(start);
        }
Add a single {@link Traverser.Admin} object to the head of the traversal. Users should typically not need
to call this method. For dynamic inject of data, they should use {@link InjectStep}.

@param start a traverser to add to the traversal
gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/process/traversal/Traversal.java