[legacy] clean up legacy code (#4743)

* [legacy] remove outdated codes of pipeline (#4692)

* [legacy] remove cli of benchmark and update optim (#4690)

* [legacy] remove cli of benchmark and update optim

* [doc] fix cli doc test

* [legacy] fix engine clip grad norm

* [legacy] remove outdated colo tensor (#4694)

* [legacy] remove outdated colo tensor

* [test] fix test import

* [legacy] move outdated zero to legacy (#4696)

* [legacy] clean up utils (#4700)

* [legacy] clean up utils

* [example] update examples

* [legacy] clean up amp

* [legacy] fix amp module

* [legacy] clean up gpc (#4742)

* [legacy] clean up context

* [legacy] clean core, constants and global vars

* [legacy] refactor initialize

* [example] fix examples ci

* [example] fix examples ci

* [legacy] fix tests

* [example] fix gpt example

* [example] fix examples ci

* [devops] fix ci installation

* [example] fix examples ci

colossalai/legacy/utils/data_sampler/base_sampler.py

@@ -0,0 +1,19 @@
+#!/usr/bin/env python
+# -*- encoding: utf-8 -*-
+
+from abc import ABC, abstractmethod
+
+
+class BaseSampler(ABC):
+
+    def __init__(self, dataset, batch_size):
+        self.dataset = dataset
+        self.batch_size = batch_size
+
+    @abstractmethod
+    def __len__(self):
+        pass
+
+    @abstractmethod
+    def __iter__(self):
+        pass