code: protected final Set<String> getAcceptedMimeTypes() {
          if (acceptedMimeTypesSet == null) {
              // No defaults are registered, so use those non-defaults ...
              acceptedMimeTypesSet = new HashSet<String>();
              for (String mimeType : acceptedMimeTypes) {
                  if (mimeType == null) continue;
                  mimeType = mimeType.trim();
                  if (mimeType.length() == 0) continue;
                  acceptedMimeTypesSet.add(mimeType);
              }
          }
          return acceptedMimeTypesSet;
      }
docs: Utility method to obtain the set of accepted MIME types. The resulting set will either be those set by default in the
  subclass' overridden {@link #initialize(NamespaceRegistry, NodeTypeManager)} method or the MIME types explicitly set in the
  sequencers configuration.
  
  @return the set of MIME types that are accepted by this Sequencer instance; never null but possibly empty if this Sequencer
  instance accepts all MIME types