def _build_estimator(tf_transform_dir, config, hidden_units=None, warm_start_from=None): """Build an estimator for predicting the tipping behavior of taxi riders. Args: tf_transform_dir: directory in which the tf-transform model was written during the preprocessing step. config: tf.contrib.learn.RunConfig defining the runtime environment for the estimator (including model_dir). hidden_units: [int], the layer sizes of the DNN (input layer first) warm_start_from: Optional directory to warm start from. Returns: Resulting DNNLinearCombinedClassifier. """ metadata_dir = os.path.join(tf_transform_dir, transform_fn_io.TRANSFORMED_METADATA_DIR) transformed_metadata = metadata_io.read_metadata(metadata_dir) transformed_feature_spec = transformed_metadata.schema.as_feature_spec() transformed_feature_spec.pop(_transformed_name(_LABEL_KEY)) real_valued_columns = [ tf.feature_column.numeric_column(key, shape=()) for key in _transformed_names(_DENSE_FLOAT_FEATURE_KEYS) ] categorical_columns = [ tf.feature_column.categorical_column_with_identity( key, num_buckets=_VOCAB_SIZE + _OOV_SIZE, default_value=0) for key in _transformed_names(_VOCAB_FEATURE_KEYS) ] categorical_columns += [ tf.feature_column.categorical_column_with_identity( key, num_buckets=_FEATURE_BUCKET_COUNT, default_value=0) for key in _transformed_names(_BUCKET_FEATURE_KEYS) ] categorical_columns += [ tf.feature_column.categorical_column_with_identity( key, num_buckets=num_buckets, default_value=0) for key, num_buckets in zip( _transformed_names(_CATEGORICAL_FEATURE_KEYS),