keras.utils.Sequence

Keras.utils.Sequence is a base class used for creating custom sequence data generators for training deep learning models in Keras. It is used to efficiently load and preprocess large datasets that might not fit entirely into memory.

A sequence is a type of generator that provides an efficient way to iterate over a large dataset. It is used to feed data to a model in batches during training, validation, or testing. The Sequence class provides an implementation of this generator that ensures thread-safe and ordered data loading.

The Sequence class requires the implementation of two methods: __getitem__ and __len__. The __getitem__ method is responsible for returning a batch of data given an index. The __len__ method returns the total number of batches in the sequence.

To create a custom Sequence, you need to subclass the Keras.utils.Sequence class and implement these two methods based on your data format and preprocessing requirements. Once the Sequence is defined, it can be used in the Keras API for training, validation, and testing.