code: @SuppressWarnings("unchecked")
    public static GrammaticalRelation valueOf(Object o) {
      if (o instanceof GrammaticalRelation) {
        return (GrammaticalRelation) o;
      } else if (o instanceof Class) {
        try {
          return getRelation((Class<? extends GrammaticalRelationAnnotation>) o);
        } catch (Exception e) {
          return null;
        }
      } else if (o instanceof String) {
        return valueOf((String) o);
      } else {
        return null;
      }
    }
docs: Returns an EnglishGrammaticalRelation based on the argument.
  It works if passed a GrammaticalRelation or the String
  representation of one (e.g. "nsubj").  It returns <code>null</code>
  for other classes or if no string match is found.
  
  @param o A GrammaticalRelation or String
  @return The EnglishGrammaticalRelation with that name