I'm trying to convert my Keras hdf5 file into a TensorFlow Lite file with the following code:

```
import tensorflow as tf

# Convert the model.
converter = tf.lite.TFLiteConverter.from_keras_model("/content/best_model_11class.hdf5")
tflite_model = converter.convert()

# Save the TF Lite model.
with tf.io.gfile.GFile('model.tflite', 'wb') as f:
  f.write(tflite_model)

```

I'm getting this error on the `from_keras_model` line:

```
---------------------------------------------------------------------------
AttributeError                            Traceback (most recent call last)
<ipython-input-14-26467c686751> in <module>()
      2 
      3 # Convert the model.
----> 4 converter = tf.lite.TFLiteConverter.from_keras_model("/content/best_model_11class.hdf5")
      5 tflite_model = converter.convert()
      6 

/usr/local/lib/python3.6/dist-packages/tensorflow/lite/python/lite.py in from_keras_model(cls, model)
    426     # to None.
    427     # Once we have better support for dynamic shapes, we can remove this.
--> 428     if not isinstance(model.call, _def_function.Function):
    429       # Pass `keep_original_batch_size=True` will ensure that we get an input
    430       # signature including the batch dimension specified by the user.

AttributeError: 'str' object has no attribute 'call'

```

How do I fix this? By the way, I'm using Google Colab.