def _merge_hash(option, opt_str, value, parser):<EOL>
if not parser.values.hashes:<EOL><INDENT>parser.values.hashes = {}  <EOL><DEDENT>try:<EOL><INDENT>algo, digest = value.split('<STR_LIT::>', <NUM_LIT:1>)<EOL><DEDENT>except ValueError:<EOL><INDENT>parser.error('<STR_LIT>'<EOL>'<STR_LIT>' %<EOL>opt_str)<EOL><DEDENT>if algo not in STRONG_HASHES:<EOL><INDENT>parser.error('<STR_LIT>' %<EOL>(opt_str, '<STR_LIT:U+002CU+0020>'.join(STRONG_HASHES)))<EOL><DEDENT>parser.values.hashes.setdefault(algo, []).append(digest)<EOL>
Given a value spelled "algo:digest", append the digest to a list
    pointed to in a dict by the algo name.