code: @Override
      public Node<OWLDataProperty> getEquivalentDataProperties(OWLDataProperty pe)
              throws InconsistentOntologyException, FreshEntitiesException,
              ReasonerInterruptedException, TimeOutException {
          throw new ReasonerInternalException(
                  "getEquivalentDataProperties not implemented");
      }
docs: Gets the set of named data properties that are equivalent to the
  specified data property expression with respect to the imports closure of
  the root ontology. The properties are returned as a
  {@link Node}.
  
  @param pe
  The data property expression whose equivalent properties are
  to be retrieved.
  @return A node containing the named data properties such that for each
  named data property <code>P</code> in the node, the set of
  reasoner axioms entails
  <code>EquivalentDataProperties(pe P)</code>. </p> If
  <code>pe</code> is a named data property then <code>pe</code>
  will be contained in the node. </p> If <code>pe</code> is
  unsatisfiable with respect to the set of reasoner axioms then the
  node representing and containing
  <code>owl:bottomDataProperty</code>, i.e. the bottom node, will
  be returned. </p> If <code>ce</code> is equivalent to
  <code>owl:topDataProperty</code> with respect to the set of
  reasoner axioms then the node representing and containing
  <code>owl:topDataProperty</code>, i.e. the top node, will be
  returned </p>.
  
  @throws InconsistentOntologyException
  if the imports closure of the root ontology is inconsistent
  @throws FreshEntitiesException
  if the signature of the data property expression is not
  contained within the signature of the imports closure of the
  root ontology and the undeclared entity policy of this
  reasoner is set to {@link FreshEntityPolicy#DISALLOW}.
  @throws ReasonerInterruptedException
  if the reasoning process was interrupted for any particular
  reason (for example if reasoning was cancelled by a client
  process)
  @throws TimeOutException
  if the reasoner timed out during a basic reasoning operation.
  See {@link #getTimeOut()}.