'Load a private key from a file
:param keyfile: The name of the key file (``bytes`` or ``unicode``)
:param filetype: (optional) The encoding of the file, default is PEM
:return: None'

def use_privatekey_file(self, keyfile, filetype=_UNSPECIFIED):

    keyfile = _path_string(keyfile)
    if (filetype is _UNSPECIFIED):
        filetype = FILETYPE_PEM
    elif (not isinstance(filetype, integer_types)):
        raise TypeError('filetype    must    be    an    integer')
    use_result = _lib.SSL_CTX_use_PrivateKey_file(self._context, keyfile, filetype)
    if (not use_result):
        self._raise_passphrase_exception()
