Sample Code

class DNNClassifier(tf.keras.Model):
 def __init__(self, feature_columns, hidden_units, n_classes):
 super(DNNClassifier, self).__init__()
 self.feature_layer = tf.keras.layers.DenseFeatures(feature_columns)
 self.hidden_layers = []
 for hidden_unit in hidden_units:
 self.hidden_layers.append(tf.keras.layers.Dense(hidden_unit))
 self.prediction_layer = tf.keras.layers.Dense(n_classes, activation='softmax')
 def call(self, inputs):
 x = self.feature_layer(inputs)
 for hidden_layer in self.hidden_layers:
 x = hidden_layer(x)
 return self.prediction_layer(x)

Stacktrace on model.fit

 /Users/yang.y/go/src/github.com/sql-machine-learning/sqlflow/sql/python/models/example.py(86)<module>()
-> model.fit(train_ds, validation_data=val_ds, epochs=model.default_training_epochs(), verbose=0)
 /Users/yang.y/go/src/github.com/sql-machine-learning/sqlflow/sql/python/models/venv/lib/python3.7/site-packages/tensorflow/python/keras/engine/training.py(794)fit()
-> initial_epoch=initial_epoch)
 /Users/yang.y/go/src/github.com/sql-machine-learning/sqlflow/sql/python/models/venv/lib/python3.7/site-packages/tensorflow/python/keras/engine/training.py(1519)fit_generator()
-> steps_name='steps_per_epoch')
 /Users/yang.y/go/src/github.com/sql-machine-learning/sqlflow/sql/python/models/venv/lib/python3.7/site-packages/tensorflow/python/keras/engine/training_generator.py(257)model_iteration()
-> batch_outs = batch_function(*batch_data)
 /Users/yang.y/go/src/github.com/sql-machine-learning/sqlflow/sql/python/models/venv/lib/python3.7/site-packages/tensorflow/python/keras/engine/training.py(1242)train_on_batch()
-> extract_tensors_from_dataset=True)
 /Users/yang.y/go/src/github.com/sql-machine-learning/sqlflow/sql/python/models/venv/lib/python3.7/site-packages/tensorflow/python/keras/engine/training.py(2507)_standardize_user_data()
-> self._set_inputs(cast_inputs)
 /Users/yang.y/go/src/github.com/sql-machine-learning/sqlflow/sql/python/models/venv/lib/python3.7/site-packages/tensorflow/python/training/tracking/base.py(456)_method_wrapper()
-> result = method(self, *args, **kwargs)
 /Users/yang.y/go/src/github.com/sql-machine-learning/sqlflow/sql/python/models/venv/lib/python3.7/site-packages/tensorflow/python/keras/engine/training.py(2779)_set_inputs()
-> outputs = self.call(inputs)
 /Users/yang.y/go/src/github.com/sql-machine-learning/sqlflow/sql/python/models/example.py(62)call()
-> x = hidden_layer(x)
 /Users/yang.y/go/src/github.com/sql-machine-learning/sqlflow/sql/python/models/venv/lib/python3.7/site-packages/tensorflow/python/keras/engine/base_layer.py(594)__call__()
-> self._maybe_build(inputs)
 /Users/yang.y/go/src/github.com/sql-machine-learning/sqlflow/sql/python/models/venv/lib/python3.7/site-packages/tensorflow/python/keras/engine/base_layer.py(1713)_maybe_build()
-> self.build(input_shapes)
> /Users/yang.y/go/src/github.com/sql-machine-learning/sqlflow/sql/python/models/venv/lib/python3.7/site-packages/tensorflow/python/keras/layers/core.py(961)build()
-> dtype = dtypes.as_dtype(self.dtype or K.floatx())

Stacktrace on model.predict

 /Users/yang.y/go/src/github.com/sql-machine-learning/sqlflow/sql/python/models/example.py(90)<module>()
-> model.predict(test_ds)
 /Users/yang.y/go/src/github.com/sql-machine-learning/sqlflow/sql/python/models/venv/lib/python3.7/site-packages/tensorflow/python/keras/engine/training.py(1147)predict()
-> callbacks=callbacks)
 /Users/yang.y/go/src/github.com/sql-machine-learning/sqlflow/sql/python/models/venv/lib/python3.7/site-packages/tensorflow/python/keras/engine/training_generator.py(257)model_iteration()
-> batch_outs = batch_function(*batch_data)
 /Users/yang.y/go/src/github.com/sql-machine-learning/sqlflow/sql/python/models/venv/lib/python3.7/site-packages/tensorflow/python/keras/engine/training_generator.py(531)predict_on_batch()
-> return model.predict_on_batch(x)
 /Users/yang.y/go/src/github.com/sql-machine-learning/sqlflow/sql/python/models/venv/lib/python3.7/site-packages/tensorflow/python/keras/engine/training.py(1365)predict_on_batch()
-> x, extract_tensors_from_dataset=True)
 /Users/yang.y/go/src/github.com/sql-machine-learning/sqlflow/sql/python/models/venv/lib/python3.7/site-packages/tensorflow/python/keras/engine/training.py(2507)_standardize_user_data()
-> self._set_inputs(cast_inputs)
 /Users/yang.y/go/src/github.com/sql-machine-learning/sqlflow/sql/python/models/venv/lib/python3.7/site-packages/tensorflow/python/training/tracking/base.py(456)_method_wrapper()
-> result = method(self, *args, **kwargs)
 /Users/yang.y/go/src/github.com/sql-machine-learning/sqlflow/sql/python/models/venv/lib/python3.7/site-packages/tensorflow/python/keras/engine/training.py(2779)_set_inputs()
-> outputs = self.call(inputs)
 /Users/yang.y/go/src/github.com/sql-machine-learning/sqlflow/sql/python/models/example.py(62)call()
-> x = hidden_layer(x)
 /Users/yang.y/go/src/github.com/sql-machine-learning/sqlflow/sql/python/models/venv/lib/python3.7/site-packages/tensorflow/python/keras/engine/base_layer.py(594)__call__()
-> self._maybe_build(inputs)
 /Users/yang.y/go/src/github.com/sql-machine-learning/sqlflow/sql/python/models/venv/lib/python3.7/site-packages/tensorflow/python/keras/engine/base_layer.py(1713)_maybe_build()
-> self.build(input_shapes)
> /Users/yang.y/go/src/github.com/sql-machine-learning/sqlflow/sql/python/models/venv/lib/python3.7/site-packages/tensorflow/python/keras/layers/core.py(961)build()
-> dtype = dtypes.as_dtype(self.dtype or K.floatx())

Conclusion