def select_files(self, what="o"):
        """
        Helper function used to select the files of a task.

        Args:
            what: string with the list of characters selecting the file type
                  Possible choices:
                    i ==> input_file,
                    o ==> output_file,
                    f ==> files_file,
                    j ==> job_file,
                    l ==> log_file,
                    e ==> stderr_file,
                    q ==> qout_file,
                    all ==> all files.
        """
        choices = collections.OrderedDict([
            ("i", self.input_file),
            ("o", self.output_file),
            ("f", self.files_file),
            ("j", self.job_file),
            ("l", self.log_file),
            ("e", self.stderr_file),
            ("q", self.qout_file),
        ])

        if what == "all":
            return [getattr(v, "path") for v in choices.values()]

        selected = []
        for c in what:
            try:
                selected.append(getattr(choices[c], "path"))
            except KeyError:
                logger.warning("Wrong keyword %s" % c)

        return selected
Helper function used to select the files of a task.

        Args:
            what: string with the list of characters selecting the file type
                  Possible choices:
                    i ==> input_file,
                    o ==> output_file,
                    f ==> files_file,
                    j ==> job_file,
                    l ==> log_file,
                    e ==> stderr_file,
                    q ==> qout_file,
                    all ==> all files.