docs: def PushSection(self, name, pre_formatters):
          """Given a section name, push it on the top of the stack.
  
      Returns:
        The new section, or None if there is no such section.
      """
          if name == '@':
              value = self.stack[-1].context
          else:
              value = self.stack[-1].context.get(name)
          
          # Apply pre-formatters
          for i, (f, args, formatter_type) in enumerate(pre_formatters):
              if formatter_type == ENHANCED_FUNC:
                  value = f(value, self, args)
              elif formatter_type == SIMPLE_FUNC:
                  value = f(value)
              else:
                  assert False, 'Invalid formatter type %r' % formatter_type
          
          self.stack.append(_Frame(value))
          return value