.. _op_ai_onnx_Optional:

Optional
========

- **Domain**: ``ai.onnx``
- **Since version**: 15

Constructs an optional-type value containing either an empty optional of a certain type specified by the attribute,
or a non-empty value containing the input element.

**Inputs**

- **input** (*V*): The input element.

**Outputs**

- **output** (*O*): The optional output enclosing the input element.

**Type Constraints**

- **V**: Constrain input type to all tensor and sequence types.
  Allowed types: seq(tensor(bool)), seq(tensor(complex128)), seq(tensor(complex64)), seq(tensor(double)), seq(tensor(float)), seq(tensor(float16)), seq(tensor(int16)), seq(tensor(int32)), seq(tensor(int64)), seq(tensor(int8)), seq(tensor(string)), seq(tensor(uint16)), seq(tensor(uint32)), seq(tensor(uint64)), seq(tensor(uint8)), tensor(bool), tensor(complex128), tensor(complex64), tensor(double), tensor(float), tensor(float16), tensor(int16), tensor(int32), tensor(int64), tensor(int8), tensor(string), tensor(uint16), tensor(uint32), tensor(uint64), tensor(uint8).
- **O**: Constrain output type to all optional tensor or optional sequence types.
  Allowed types: optional(seq(tensor(bool))), optional(seq(tensor(complex128))), optional(seq(tensor(complex64))), optional(seq(tensor(double))), optional(seq(tensor(float))), optional(seq(tensor(float16))), optional(seq(tensor(int16))), optional(seq(tensor(int32))), optional(seq(tensor(int64))), optional(seq(tensor(int8))), optional(seq(tensor(string))), optional(seq(tensor(uint16))), optional(seq(tensor(uint32))), optional(seq(tensor(uint64))), optional(seq(tensor(uint8))), optional(tensor(bool)), optional(tensor(complex128)), optional(tensor(complex64)), optional(tensor(double)), optional(tensor(float)), optional(tensor(float16)), optional(tensor(int16)), optional(tensor(int32)), optional(tensor(int64)), optional(tensor(int8)), optional(tensor(string)), optional(tensor(uint16)), optional(tensor(uint32)), optional(tensor(uint64)), optional(tensor(uint8)).

Examples
--------

**test_cc_optional**

.. code-block:: text

    Attributes:
      type = <attribute type 13>

.. code-block:: text

    Inputs:
      input: shape=(2, 3), dtype=float32
        [[-1.  ,  0.  ,  1.5 ],
         [-2.25,  3.5 , -4.75]]

    Outputs:
      output: shape=(2, 3), dtype=float32
        [[-1.  ,  0.  ,  1.5 ],
         [-2.25,  3.5 , -4.75]]