def _get_digest(self, info):
result = None<EOL>for algo in ('<STR_LIT>', '<STR_LIT>'):<EOL><INDENT>key = '<STR_LIT>' % algo<EOL>if key in info:<EOL><INDENT>result = (algo, info[key])<EOL>break<EOL><DEDENT><DEDENT>return result<EOL>
Get a digest from a dictionary by looking at keys of the form
'algo_digest'.

Returns a 2-tuple (algo, digest) if found, else None. Currently
looks only for SHA256, then MD5.