code: protected static Orientation parseGlobalOrientation(String v) {
          if (v == null) {
              return null;
          }
          if (isDirectedString(v)) {
              return Orientation.DIRECTED;
          } else if (isReversedString(v)) {
              return Orientation.REVERSED;
          } else if (isUndirectedString(v)) {
              return Orientation.UNDIRECTED;
          } else {
              throw new IllegalArgumentException(ORIENTATION_ERROR);
          }
      }
docs: Recovers the global orientation from a string.
  
  
  @param v String
  @return The global orientation