'load class names from text file
Parameters:
filename: str
file stores class names
dirname: str
file directory'

def _load_class_names(self, filename, dirname):

    full_path = osp.join(dirname, filename)
    classes = []
    with open(full_path, 'r') as f:
        classes = [l.strip() for l in f.readlines()]
    return classes
