@staticmethod<EOL><INDENT>def from_string(key, password='<STR_LIT>'):<DEDENT>
parsed_pem_key = _helpers._parse_pem_key(_helpers._to_bytes(key))<EOL>if parsed_pem_key:<EOL><INDENT>pkey = RSA.importKey(parsed_pem_key)<EOL><DEDENT>else:<EOL><INDENT>raise NotImplementedError(<EOL>'<STR_LIT>'<EOL>'<STR_LIT>'<EOL>'<STR_LIT>')<EOL><DEDENT>return PyCryptoSigner(pkey)<EOL>
Construct a Signer instance from a string.

        Args:
            key: string, private key in PEM format.
            password: string, password for private key file. Unused for PEM
                      files.

        Returns:
            Signer instance.

        Raises:
            NotImplementedError if the key isn't in PEM format.