code: def get_properties_from_graph(graph):
          
          # collapse to single list
          property_set = set()
          for row in graph.predicates():
              property_set.add(row)
  
          return property_set
docs: Wrapper for RDFLib.graph.predicates() that returns a unique set
          :param graph: RDFLib.graph
          :return: set, set of properties