docs: def weld_select_from_struct(struct_of_vec, index_to_select):
      """Select a single vector from the struct of vectors.
  
      Parameters
      ----------
      struct_of_vec : WeldObject
          Encoding a struct of vectors.
      index_to_select : int
          Which vec to select from the struct.
  
      Returns
      -------
      WeldObject
          Representation of this computation.
  
      """
      obj_id, weld_obj = create_weld_object(struct_of_vec)
  
      weld_template = '{struct}.${index}'
  
      weld_obj.weld_code = weld_template.format(struct=obj_id,
                                                index=index_to_select)
  
      return weld_obj