add doc for trace indice

colossalai/autochunk/trace_indice.py

 import copy
+from typing import Dict, List, Tuple
 
-from .utils import (
-    find_idx_by_name,
-    get_node_shape,
-)
+from torch.fx.node import Node
+
+from .utils import find_idx_by_name, get_node_shape
 
 
 class TraceIndice(object):
-    def __init__(self, node_list) -> None:
+    """
+    Trace all indice infomation for every node.
+
+    Indice is a logical concept. Equal dims can been treated as one indice.
+    eg. dim(x1) = [a, b, c]
+        dim(x2) = [d, e, f]
+        and we have x3 = x1 * x2.
+        then a=d, b=e, c=f, due to the broadcast property,
+        dim(x1)=dim(x2)=dim(x3)=[a, b, c]
+    This class will record every node's dims' indice, compute and source.
+
+    Attibutes:
+        node_list (List)
+        indice_trace_list (List): [{"indice": [...], "compute": [...], "source": [...]}, {...}]
+        indice_view_list (Dict): not used for now
+        indice_count (int): record indice number
+
+    Args:
+        node_list (List)
+    """
+
+    def __init__(self, node_list: List) -> None:
         self.node_list = node_list
         self.indice_trace_list = self._init_indice_trace_list()
         self.indice_view_list = {}