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Base class for decoders that turns a list of bytes to (composite) tensors.

Sub-classes must implement decode_record() (see its docstring for requirements).

Decoder instances can be saved as a SavedModel by save_decoder(). The SavedModel can be loaded back by load_decoder(). However, the loaded decoder will always be of the type LoadedDecoder and only have the public interfaces listed in this base class available.

record_index_tensor_name The name of the tensor indicating which record a slice is from.

The decoded tensors are batch-aligned among themselves, but they don't necessarily have to be batch-aligned with the input records. If not, sub-classes should implement this method to tie the batch dimension with the input record.

The record index tensor must be a SparseTensor or a RaggedTensor of integral type, and must be 2-D and must not contain "missing" values.

A record index tensor like the following: [[0], [0], [2]] means that of 3 "rows" in the output "batch", the first two rows came from the first record, and the 3rd row came from the third record.

The name must not be an empty string.



Sub-classes should implement this.

Implementations must use TF ops to derive the result (composite) tensors, as this function will be traced and become a tf.function (thus a TF Graph). Note that autograph is not enabled in such tracing, which means any python control flow / loops will not be converted to TF cond / loops automatically.

The returned tensors must be batch-aligned (i.e. they should be at least of rank 1, and their outer-most dimensions must be of the same size). They do not have to be batch-aligned with the input tensor, but if that's the case, an additional tensor must be provided among the results, to indicate which input record a "row" in the output batch comes from. See record_index_tensor_name for more details.

records a 1-D string tensor that contains the records to be decoded.

A dict of (composite) tensors.


Returns the tf.TypeSpecs of the decoded tensors.

A dict whose keys are the same as keys of the dict returned by decode_record() and values are the tf.TypeSpec of the corresponding (composite) tensor.