code: def append_field(self, path, name, value):
          
          path = make_path(path)
          container = self.get_container(path)
          current = container._values.get(name, None)
          if current is None:
              container._values[name] = value
          elif isinstance(current, ValueTree):
              raise TypeError()
          elif isinstance(current, list):
              container._values[name] = current + [value]
          else:
              container._values[name] = [current, value]
docs: Appends the field to the container at the specified path.
  
          :param path: str or Path instance
          :param name:
          :type name: str
          :param value:
          :type value: str