[tutorial] edited hands-on practices (#1899)

* Add handson to ColossalAI.

* Change names of handsons and edit sequence parallel example.

* Edit wrong folder name

* resolve conflict

* delete readme

examples/tutorial/sequence_parallel/model/layers/init_method.py

@@ -0,0 +1,12 @@
+import torch
+import math
+
+def init_normal(tensor, sigma):
+    """Init method based on N(0, sigma)."""
+    torch.nn.init.normal_(tensor, mean=0.0, std=sigma)
+
+
+def output_init_normal(tensor, sigma, num_layers):
+    """Init method based on N(0, sigma/sqrt(2*num_layers)."""
+    std = sigma / math.sqrt(2.0 * num_layers)
+    torch.nn.init.normal_(tensor, mean=0.0, std=std)