docs: def text(self):
          """Formatted API declarations.
  
          Equivalent to the concatenation of `text` attributes of
          types, enums and commands in this Registry.
          """
          out = []
          out.extend(x.text for x in self.types.values())
          out.extend(x.text for x in self.enums.values())
          out.extend('extern {0};'.format(x.text)
                     for x in self.commands.values())
          return '\n'.join(out)