code: @Override
      public boolean hasStatement(Statement st, boolean includeInferred, Resource... contexts) throws RepositoryException {
          return hasStatement(st.getSubject(),st.getPredicate(),st.getObject(),includeInferred,contexts);
      }
docs: returns true or false if a statement exists in repository / context
  
  @param st
  @param includeInferred
  @param contexts
  @return boolean
  @throws RepositoryException