code: def get_property_names(self):
          '''
          Returns all property names in this collection of signatures
          '''
          property_names = set()
          for signature_value in self.values():
              for property_name in signature_value.keys():
                  property_names.add(property_name)
          return property_namef get_property_names(self):
          '''
          Returns all property names in this collection of signatures
          '''
          property_names = set()
          for signature_value in self.values():
              for property_name in signature_value.keys():
                  property_names.add(property_name)
          return property_names
docs: Returns all property names in this collection of signatures