Import issue: no auto completion under certain conditions

1. If I use

import tensorflow as tf

tf.keras.layers.Conv2D

the auto completion works for completing Conv2D.

2. However, if I use import like:

import tensorflow.keras.layers

layers.Conv2D

No completion helper shows for Conv2D and any other functions/classes.

3. The completion will also fail if I type:

from tensorflow.keras.layers import Conv2D

No completion helper shows for commands after the import keyword.

Is it because of internal limit in the auto completion module?