Specifies the rank, dtype and shape of every input to a layer.

Layers can expose (if appropriate) an input_spec attribute: an instance of InputSpec, or a nested structure of InputSpec instances (one per input tensor). These objects enable the layer to run input compatibility checks for input structure, input rank, input shape, and input dtype.

A None entry in a shape is compatible with any dimension, a None shape is compatible with any shape.

dtype Expected DataType of the input.
shape Shape tuple, expected shape of the input (may include None for unchecked axes). Includes the batch size.
ndim Integer, expected rank of the input.
max_ndim Integer, maximum rank of the input.
min_ndim Integer, minimum rank of the input.