TPU version of tf.compat.v1.feature_column.embedding_column.
tf.compat.v1.tpu.experimental.embedding_column(
    categorical_column, dimension, combiner='mean', initializer=None,
    max_sequence_length=0, learning_rate_fn=None, embedding_lookup_device=None,
    tensor_core_shape=None
)
Note that the interface for tf.tpu.experimental.embedding_column is
different from that of tf.compat.v1.feature_column.embedding_column: The
following arguments are NOT supported: ckpt_to_load_from,
tensor_name_in_ckpt, max_norm and trainable.
Use this function in place of tf.compat.v1.feature_column.embedding_column
when you want to use the TPU to accelerate your embedding lookups via TPU
embeddings.
column = tf.feature_column.categorical_column_with_identity(...)
tpu_column = tf.tpu.experimental.embedding_column(column, 10)
...
def model_fn(features):
  dense_feature = tf.keras.layers.DenseFeature(tpu_column)
  embedded_feature = dense_feature(features)
  ...
estimator = tf.estimator.tpu.TPUEstimator(
    model_fn=model_fn,
    ...
    embedding_config_spec=tf.estimator.tpu.experimental.EmbeddingConfigSpec(
      column=[tpu_column],
      ...))
Args | 
categorical_column
 | 
A categorical column returned from
categorical_column_with_identity, weighted_categorical_column,
categorical_column_with_vocabulary_file,
categorical_column_with_vocabulary_list,
sequence_categorical_column_with_identity,
sequence_categorical_column_with_vocabulary_file,
sequence_categorical_column_with_vocabulary_list
 | 
dimension
 | 
An integer specifying dimension of the embedding, must be > 0.
 | 
combiner
 | 
A string specifying how to reduce if there are multiple entries
in a single row for a non-sequence column. For more information, see
tf.feature_column.embedding_column.
 | 
initializer
 | 
A variable initializer function to be used in embedding
variable initialization. If not specified, defaults to
tf.compat.v1.truncated_normal_initializer with mean 0.0 and
standard deviation 1/sqrt(dimension).
 | 
max_sequence_length
 | 
An non-negative integer specifying the max sequence
length. Any sequence shorter then this will be padded with 0 embeddings
and any sequence longer will be truncated. This must be positive for
sequence features and 0 for non-sequence features.
 | 
learning_rate_fn
 | 
A function that takes global step and returns learning
rate for the embedding table.
 | 
embedding_lookup_device
 | 
The device on which to run the embedding lookup.
Valid options are "cpu", "tpu_tensor_core", and "tpu_embedding_core".
If specifying "tpu_tensor_core", a tensor_core_shape must be supplied.
If not specified, the default behavior is embedding lookup on
"tpu_embedding_core" for training and "cpu" for inference.
Valid options for training : ["tpu_embedding_core", "tpu_tensor_core"]
Valid options for serving :  ["cpu", "tpu_tensor_core"]
For training, tpu_embedding_core is good for large embedding vocab (>1M),
otherwise, tpu_tensor_core is often sufficient.
For serving, doing embedding lookup on tpu_tensor_core during serving is
a way to reduce host cpu usage in cases where that is a bottleneck.
 | 
tensor_core_shape
 | 
If supplied, a list of integers which specifies
the intended dense shape to run embedding lookup for this feature on
TensorCore. The batch dimension can be left None or -1 to indicate
a dynamic shape. Only rank 2 shapes currently supported.
 | 
Returns | 
A  _TPUEmbeddingColumnV2.
 | 
Raises | 
ValueError
 | 
if dimension not > 0.
 | 
ValueError
 | 
if initializer is specified but not callable.
 |