code: def add_properties(self, filename):
          
          filename = os.path.expanduser(filename)
          if os.path.exists(filename):
              with open(filename, 'r') as yaml_file:
                  self.update_properties(yaml.safe_load(yaml_file))
docs: Add properties to config based on filename replacing previous values.
          :param filename: str path to YAML file to pull top level properties from