如何从DataFrame创建一个tf.data.Dataset，其中一列的每个条目都是一个固定长度的Numpy数组或列表？

import tensorflow as tf
import pandas as pd
import numpy as np

data = {'col1': [np.array([1, 2, 3]), np.array([4, 5, 6]), np.array([7, 8, 9])],
        'col2': ['a', 'b', 'c']}
df = pd.DataFrame(data)

def row_to_dict(row):
    return {'col1': row['col1'], 'col2': row['col2']}

dataset = tf.data.Dataset.from_tensor_slices(df.apply(row_to_dict, axis=1).values)

dataset = dataset.batch(batch_size)
dataset = dataset.shuffle(buffer_size)
dataset = dataset.repeat(num_epochs)