code: def write_to(self, group, append=False):
          
          write_index(self, group, append)
          self._entries['items'].write_to(group)
          self._entries['features'].write_to(group, append)
          self._entries['labels'].write_to(group)
          if self.has_properties():
              self._entries['properties'].write_to(group, append=append)
docs: Write the data to the given group.
  
          :param h5py.Group group: The group to write the data on. It is
              assumed that the group is already existing or initialized
              to store h5features data (i.e. the method
              ``Data.init_group`` have been called.
  
          :param bool append: If False, any existing data in the group
              is overwrited. If True, the data is appended to the end of
              the group and we assume ``Data.is_appendable_to`` is True
              for this group.