code: def _next_label(self):
          
          # Special case for the very first label.
          if self.page_count == 0:
              self._new_page()
  
          # Filled up a page.
          elif self._position == self._numlabels:
              self._new_page()
  
          # Filled up a row.
          elif self._position[1] == self.specs.columns:
              self._position[0] += 1
              self._position[1] = 0
  
          # Move to the next column.
          self._position[1] += 1
docs: Helper method to move to the next label. Not intended for external use.
  
          This does not increment the label_count attribute as the next label may
          not be usable (it may have been marked as missing through
          partial_pages). See _next_unused_label for generally more useful method.