@Override
    public String getStepName() { return "split(local)"; }
Reference implementation for substring step, a mid-traversal step which returns a list of strings created by
splitting the incoming string traverser around the matches of the given separator. A null separator will split the
string by whitespaces. Null values from incoming traversers are not processed and remain as null when returned.
If the incoming traverser is a non-String value then an {@code IllegalArgumentException} will be thrown.

@author David Bechberger (http://bechberger.com)
@author Yang Xia (http://github.com/xiazcy)
gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/process/traversal/step/map/SplitLocalStep.java