docs: def pretty(self, indent=1, debug=False):
          """
          Return a pretty formatted representation of self.
          Include additional debug details if `debug` is True.
          """
          debug_details = ''
          if debug:
              debug_details += '<isliteral=%r, iscanonical=%r>' % (self.isliteral, self.iscanonical)
          if self.isliteral:
              pretty_literal = self.args[0].pretty(indent=0, debug=debug)
              return (' ' * indent) + '%s(%s%s)' % (self.__class__.__name__, debug_details, pretty_literal)
          else:
              return super(NOT, self).pretty(indent=indent, debug=debug)