docs: def _do_attr(self, n, value):
          ''''_do_attr(self, node) -> None
          Process an attribute.'''
  
          W = self.write
          W(' ')
          W(n)
          W('="')
          s = string.replace(value, "&", "&amp;")
          s = string.replace(s, "<", "&lt;")
          s = string.replace(s, '"', '&quot;')
          s = string.replace(s, '\011', '&#x9')
          s = string.replace(s, '\012', '&#xA')
          s = string.replace(s, '\015', '&#xD')
          W(s)
          W('"')