def METHOD_NAME(self):
    """
    To delete backup files
    """
    dir_name, _ = os.path.split(self.baseFilename)
    file_names = os.listdir(dir_name)
    result = []
    prefix = self.prefix + '-'
    for file_name in file_names:
        if file_name[:len(prefix)] == prefix:
            suffix = file_name[len(prefix):-4]
            if re.compile(self.extMath).match(suffix):
                result.append(os.path.join(dir_name, file_name))
    result.sort()
    if len(result) < self.backupCount:
        result = []
    else:
        result = result[:len(result) - self.backupCount]
    return result