old_contents: #Copyright (c) 2011-2013, Walter Bender
  
  # This procedure is invoked when the user-definable block on the
  # "extras" palette is selected.
  
  # Usage: Import this code into a Python (user-definable) block; when
  # it is run, a u-turn block will be added to the Turtle Palette. You
  # can use the u-turn block as you would any other block.
  
  
  def myblock(tw, arg):
      ''' Add a uturn block to the 'turtle' palette '''
  
      # def_prim takes 3 arguments: the primitive name, the number of
      # arguments -- 0 in this case -- and the function to call -- in this
      # case, we define the _prim_uturn function to set heading += 180.
      def _prim_uturn(tw):
          value = tw.turtles.get_active_turtle().get_heading() + 180
          tw.turtles.get_active_turtle().set_heading(value)
          # We also update the label on the heading block to indicate
          # the current heading value
          if tw.lc.update_values:
              tw.lc.update_label_value('heading', value)
  
      from TurtleArt.tapalette import make_palette, palette_name_to_index
      from TurtleArt.talogo import primitive_dictionary
      from gettext import gettext as _
  
      # Choose a palette for the new block.
      palette = make_palette('turtle')
  
      # Create a new block prototype.
      palette.add_block('uturn',
                        style='basic-style-extended-vertical',
                        label=_('uturn'),
                        prim_name='uturn',
                        help_string=_('make a uturn'))
  
      # Add its primitive to the LogoCode dictionary.
      tw.lc.def_prim('uturn', 0, lambda self: _prim_uturn(tw))
  
      # Regenerate the palette, which will now include the new block.
      tw.show_toolbar_palette(palette_name_to_index('turtle'),
                              regenerate=True)
  
      palette.add_block('uturn',  # the name of your block
                        style='basic-style',  # the block style
                        label=_('u turn'),  # the label for the block
                        prim_name='uturn',  # code reference (see below)
                        help_string=_('turns the turtle 180 degrees'))
  
new_contents: #Copyright (c) 2011-2013, Walter Bender
  
  # This procedure is invoked when the user-definable block on the
  # "extras" palette is selected.
  
  # Usage: Import this code into a Python (user-definable) block; when
  # it is run, a u-turn block will be added to the Turtle Palette. You
  # can use the u-turn block as you would any other block.
  
  
  def myblock(tw, arg):
      ''' Add a uturn block to the 'turtle' palette '''
  
      # def_prim takes 3 arguments: the primitive name, the number of
      # arguments -- 0 in this case -- and the function to call -- in this
      # case, we define the _prim_uturn function to set heading += 180.
      def _prim_uturn(tw):
          value = tw.turtles.get_active_turtle().get_heading() + 180
          tw.turtles.get_active_turtle().set_heading(value)
          # We also update the label on the heading block to indicate
          # the current heading value
          if tw.lc.update_values:
              tw.lc.update_label_value('heading', value)
  
      from TurtleArt.tapalette import make_palette, palette_name_to_index
      from TurtleArt.talogo import primitive_dictionary
      from gettext import gettext as _
  
      # Choose a palette for the new block.
      palette = make_palette('turtle')
  
      # Create a new block prototype.
      palette.add_block('uturn',
                        style='basic-style-extended-vertical',
                        label=_('uturn'),
                        prim_name='uturn',
                        help_string=_('turns the turtle 180 degrees'))
  
      # Add its primitive to the LogoCode dictionary.
      tw.lc.def_prim('uturn', 0, lambda self: _prim_uturn(tw))
  
      # Regenerate the palette, which will now include the new block.
      tw.show_toolbar_palette(palette_name_to_index('turtle'),
                              regenerate=True)
  
subject: remove redundant add_block and make spelling match (#4541)