validation: a module used for command line arguments validation

validation.get_parser_if_valid(args)

Parses the command line arguments and returns a CNV parser if they are valid.

Checks if --base_dir is a directory and has a corresponding --format. Also verifies that a --family was given when using the --picke argument.

This function returns a parsers.ParentParser subclass corresponding to the --format (or a pickle parser if using the --pickle option.