code: public boolean containsDirectoryOfType(Class<? extends Directory> type)
      {
          for (Directory dir : _directories) {
              if (type.isAssignableFrom(dir.getClass()))
                  return true;
          }
          return false;
      }
docs: Indicates whether an instance of the given directory type exists in this Metadata instance.
  
  @param type the {@link Directory} type
  @return <code>true</code> if a {@link Directory} of the specified type exists, otherwise <code>false</code>