Some bugs in submixes function [Fixed]

[shawn120]

Update: I fixed this issues and did a pull request.

I am trying to use the submixes function on the babyslakh dataset, but there are few bugs.
First thing is that arguments option '-submix-definition-file', '-s' and '-src-dir', '-s' have the same short name so that cause option string conflict. And from the 124 line:

if args.root_dir is None and args.src_dir is None:
    raise ValueError('Must provide one of (root_dir, src_dir).')
elif args.root_dir is not None and args.src_dir is not None:
    raise ValueError('Must provide only one of (root_dir, src_dir).')

the attribute name should be input_dir instead of root_dir
Besides that there are still some bugs which prevent this code from working.

Did I use this code wrong or this function is still half-way finished?