def get_ext(name):
other, sep, ext = name.partition('<STR_LIT:.>')<EOL>return ext<EOL>
Return the extension only for a name (like a filename)

>>> get_ext('foo.bar')
'bar'
>>> get_ext('.only')
'only'
>>> get_ext('')
''
>>> get_ext('noext')
''
>>> get_ext('emptyext.')
''

Note that for any non-empty string, the result will never be the
same as the input. This is a useful property for basepack.