[legacy] move trainer to legacy (#4545)

* [legacy] move trainer to legacy

* [doc] update docs related to trainer

* [test] ignore legacy test

colossalai/legacy/trainer/hooks/_base_hook.py

@@ -0,0 +1,106 @@
+#!/usr/bin/env python
+# -*- encoding: utf-8 -*-
+
+from abc import ABC
+
+from torch import Tensor
+
+
+class BaseHook(ABC):
+    """This class allows users to add desired actions in specific time points
+    during training or evaluation.
+
+    :param priority: Priority in the printing, hooks with small priority will be printed in front
+    :type priority: int
+    """
+
+    def __init__(self, priority: int) -> None:
+        self.priority = priority
+
+    def after_hook_is_attached(self, trainer):
+        """Actions after hooks are attached to trainer.
+        """
+        pass
+
+    def before_train(self, trainer):
+        """Actions before training.
+        """
+        pass
+
+    def after_train(self, trainer):
+        """Actions after training.
+        """
+        pass
+
+    def before_train_iter(self, trainer):
+        """Actions before running a training iteration.
+        """
+        pass
+
+    def after_train_iter(self, trainer, output: Tensor, label: Tensor, loss: Tensor):
+        """Actions after running a training iteration.
+
+        Args:
+           trainer (:class:`Trainer`): Trainer which is using this hook.
+           output (:class:`torch.Tensor`): Output of the model.
+           label (:class:`torch.Tensor`): Labels of the input data.
+           loss (:class:`torch.Tensor`): Loss between the output and input data.
+        """
+        pass
+
+    def before_train_epoch(self, trainer):
+        """Actions before starting a training epoch.
+        """
+        pass
+
+    def after_train_epoch(self, trainer):
+        """Actions after finishing a training epoch.
+        """
+        pass
+
+    def before_test(self, trainer):
+        """Actions before evaluation.
+        """
+        pass
+
+    def after_test(self, trainer):
+        """Actions after evaluation.
+        """
+        pass
+
+    def before_test_epoch(self, trainer):
+        """Actions before starting a testing epoch.
+        """
+        pass
+
+    def after_test_epoch(self, trainer):
+        """Actions after finishing a testing epoch.
+        """
+        pass
+
+    def before_test_iter(self, trainer):
+        """Actions before running a testing iteration.
+        """
+        pass
+
+    def after_test_iter(self, trainer, output: Tensor, label: Tensor, loss: Tensor):
+        """Actions after running a testing iteration.
+
+        Args:
+           trainer (:class:`Trainer`): Trainer which is using this hook
+           output (:class:`torch.Tensor`): Output of the model
+           label (:class:`torch.Tensor`): Labels of the input data
+           loss (:class:`torch.Tensor`): Loss between the output and input data
+        """
+        pass
+
+    def init_runner_states(self, trainer, key, val):
+        """Initializes trainer's state.
+
+        Args:
+            trainer (:class:`Trainer`): Trainer which is using this hook
+            key: Key of state to be reset
+            val: Value of state to be reset
+        """
+        if key not in trainer.states:
+            trainer.states[key] = val