code: def align(value):
          
          if value.value:
              _assert_is_type('shape.value', value.value, str_types)
              if value.value not in PropertySet._valid_align:
                  raise ValueError(value.value + ' is not a valid alignment')
docs: ValueRef : string, horizontal alignment of mark
  
          Possible values are ``'left'``, ``'right'``, and ``'center'``. Only
          used if ``type`` is ``'image'`` or ``'text'``.