code: public Object loadProvUnknownGraph(String filename) {
  
          try {
              Utility u = new Utility();
              CommonTree tree = u.convertASNToTree(filename);
              Object o = u.convertTreeToJavaBean(tree, pFactory);
              if (o != null) {
                  return o;
              }
          } catch (RecognitionException t1) {
              // OK, we failed, let's try next format.
          } catch (IOException e) {
              // OK, we failed, let's try next format.
          }
          try {
              File in = new File(filename);
              ProvDeserialiser deserial = ProvDeserialiser
                      .getThreadProvDeserialiser();
              Document c = deserial.deserialiseDocument(in);
              if (c != null) {
                  return c;
              }
          } catch (JAXBException t2) {
              // OK, we failed, let's try next format.
          }
  
          try {
              Document o = new org.openprovenance.prov.json.Converter(pFactory)
                      .readDocument(filename);
              if (o != null) {
                  return o;
              }
          } catch (IOException e) {
              // OK, we failed, let's try next format.
  
          }
          try {
              org.openprovenance.prov.rdf.Utility rdfU = new org.openprovenance.prov.rdf.Utility(
                      pFactory, onto);
              Document doc = rdfU.parseRDF(filename);
              if (doc != null) {
                  return doc;
              }
          } catch (RDFParseException e) {
          } catch (RDFHandlerException e) {
          } catch (IOException e) {
          } catch (JAXBException e) {
          }
          System.out.println("Unparseable format " + filename);
          throw new UnsupportedOperationException();
  
      }
docs: Experimental code, trying to load a document without knowing its serialization format.
  First parser that succeeds returns a results. Not a robust method!
  @param filename a file to load the provenance document from
  @return a document