Supporting `*.safetensors` format.

If a model file exists with extension `.safetensors` then we can load it
more safely than with PyTorch weights.

modules/sd_models.py

@@ -45,7 +45,7 @@ def checkpoint_tiles():
 
 def list_models():
     checkpoints_list.clear()
-    model_list = modelloader.load_models(model_path=model_path, command_path=shared.cmd_opts.ckpt_dir, ext_filter=[".ckpt"])
+    model_list = modelloader.load_models(model_path=model_path, command_path=shared.cmd_opts.ckpt_dir, ext_filter=[".ckpt", ".safetensors"])
 
     def modeltitle(path, shorthash):
         abspath = os.path.abspath(path)
@@ -180,7 +180,14 @@ def load_model_weights(model, checkpoint_info, vae_file="auto"):
         # load from file
         print(f"Loading weights [{sd_model_hash}] from {checkpoint_file}")
 
-        pl_sd = torch.load(checkpoint_file, map_location=shared.weight_load_location)
+        if checkpoint_file.endswith(".safetensors"):
+            try:
+                from safetensors.torch import load_file
+            except ImportError as e:
+                raise ImportError(f"The model is in safetensors format and it is not installed, use `pip install safetensors`: {e}")
+            pl_sd = load_file(checkpoint_file, device=shared.weight_load_location)
+        else:
+            pl_sd = torch.load(checkpoint_file, map_location=shared.weight_load_location)
         if "global_step" in pl_sd:
             print(f"Global Step: {pl_sd['global_step']}")