Added example in the tutorial page for batched datasets

docs/tutorials.md

@@ -113,3 +113,66 @@ def main():
 if __name__ == "__main__":
     main()
 ```
+
+## Integrating bs-scheduler with already batched data
+
+Using already batched data disables the automated batching features of the PyTorch DataLoaders.
+In this case, a `BatchSizeManager` must be implemented by the end user to enable Batch Size Schedulers to change the batch size.
+The `CustomBatchSizeManager` can be used when the dataset class implements the `get_batch_size` and `change_batch_size` 
+methods, similar to the example below:
+
+```python
+from bs_scheduler import StepBS
+from bs_scheduler.batch_size_schedulers import CustomBatchSizeManager
+from torch import Tensor
+import torch
+from torch.utils.data import Dataset, DataLoader
+
+
+
+class BatchedDataset(Dataset):
+    def __init__(self, data: Tensor, batch_size: int):
+        self.data = data
+        self.batch_size = batch_size
+
+    def __len__(self) -> int:
+        return len(self.data) // self.batch_size
+
+    def __getitem__(self, i: int) -> Tensor:
+        return self.data[i * self.batch_size: (i + 1) * self.batch_size]
+
+    def get_batch_size(self) -> int:
+        return self.batch_size
+
+    def change_batch_size(self, batch_size: int):
+        self.batch_size = batch_size
+
+
+dataset = BatchedDataset(torch.rand(10000, 128), batch_size=100)
+dataloader = DataLoader(dataset, batch_size=None)
+scheduler = StepBS(dataloader,
+                   step_size=2,
+                   gamma=2.0,
+                   batch_size_manager=CustomBatchSizeManager(dataset),
+                   max_batch_size=10000)
+
+
+for epoch in range(10):
+    for batched_data in dataloader:
+        pass
+    print(f"There are {len(dataloader)} batches in epoch {epoch}.")
+    scheduler.step()
+```
+Output:
+```
+There are 100 batches in epoch 0.
+There are 100 batches in epoch 1.
+There are 50 batches in epoch 2.
+There are 50 batches in epoch 3.
+There are 25 batches in epoch 4.
+There are 25 batches in epoch 5.
+There are 12 batches in epoch 6.
+There are 12 batches in epoch 7.
+There are 6 batches in epoch 8.
+There are 6 batches in epoch 9.
+```