Default file path retrieval function.
        sprinter() - Generates file path list using pool processing and Queues
        crawler() - Generates file path list using os.walk() in sequence

def walk(self):
        """
        Default file path retrieval function.
        sprinter() - Generates file path list using pool processing and Queues
        crawler() - Generates file path list using os.walk() in sequence
        """
        if self.parallelize:
            self.filepaths = Sprinter(self.directory, self.filters, self.full_paths, self.pool_size, self._printer).sprinter()
        else:
            self.filepaths = Crawler(self.directory, self.filters, self.full_paths, self.topdown, self._printer).crawler()
        return self._get_filepaths()