code: def new_union(self, type, name):
          
          self._message_stack.append(UnionTemplate(type, name, self._current_container))
docs: Defines a new union to template of `type` and `name`.
  
          Fields inside the union are alternatives and the length of the union is
          the length of its longest field.
  
          Example:
          | New union | IntOrAddress | foo |
          | Chars | 16 | ipAddress |
          | u32   | int |
          | End union |