'Add certificate to chain
:param certobj: The X509 certificate object to add to the chain
:return: None'

def add_extra_chain_cert(self, certobj):

    if (not isinstance(certobj, X509)):
        raise TypeError('certobj    must    be    an    X509    instance')
    copy = _lib.X509_dup(certobj._x509)
    add_result = _lib.SSL_CTX_add_extra_chain_cert(self._context, copy)
    if (not add_result):
        _lib.X509_free(copy)
        _raise_current_error()
