code: def close_buffer(self):
          
          eb = self.active_editor_buffer
  
          # Remove this buffer.
          index = self.editor_buffers.index(eb)
          self.editor_buffers.remove(eb)
  
          # Close the active window.
          self.active_tab.close_active_window()
  
          # Close all the windows that still have this buffer open.
          for i, t in enumerate(self.tab_pages[:]):
              t.close_editor_buffer(eb)
  
              # Remove tab when there are no windows left.
              if t.window_count() == 0:
                  self.tab_pages.remove(t)
  
                  if i >= self.active_tab_index:
                      self.active_tab_index = max(0, self.active_tab_index - 1)
  
          # When there are no windows/tabs left, create a new tab.
          if len(self.tab_pages) == 0:
              self.active_tab_index = None
  
              if len(self.editor_buffers) > 0:
                  # Open the previous buffer.
                  new_index = (len(self.editor_buffers) + index - 1) % len(self.editor_buffers)
                  eb = self.editor_buffers[new_index]
  
                  # Create a window for this buffer.
                  self.tab_pages.append(TabPage(Window(eb)))
                  self.active_tab_index = 0
              else:
                  # Create a new buffer. (This will also create the window
                  # automatically.)
                  eb = self._get_or_create_editor_buffer()
docs: Close current buffer. When there are other windows showing the same
          buffer, they are closed as well. When no windows are left, the previous
          buffer or an empty buffer is shown.