code: def pin(self, hostname, x509):
          
  
          key = self._x509_key(x509)
          self._storage.setdefault(hostname, set()).add(key)
docs: Pin an :class:`OpenSSL.crypto.X509` object `x509` for use with the
          given `hostname`. Which information exactly is used to identify the
          certificate depends :meth:`_x509_key`.