code: def make_key_url(self, key):
          
          if type(key) is bytes:
              key = key.decode('utf-8')
          buf = io.StringIO()
          buf.write(u'keys')
          if not key.startswith(u'/'):
              buf.write(u'/')
          buf.write(key)
          return self.make_url(buf.getvalue())
docs: Gets a URL for a key.