Fix the prefix for OPT model in opt_modelling.py #2370 (CI RUN) (#2371)

* Fix the bug

* fix: run lints

* fix: small syntax tweak

---------
Co-authored-by: Sadra Barikbin <sadraqazvin1@yahoo.com>

integration-tests/models/test_opt.py

+import pytest
+
+
+@pytest.fixture(scope="module")
+def opt_sharded_handle(launcher):
+    with launcher("facebook/opt-6.7b", num_shard=2) as handle:
+        yield handle
+
+
+@pytest.fixture(scope="module")
+async def opt_sharded(opt_sharded_handle):
+    await opt_sharded_handle.health(300)
+    return opt_sharded_handle.client
+
+
+@pytest.mark.release
+@pytest.mark.asyncio
+async def test_opt(opt_sharded):
+    pass

server/text_generation_server/models/custom_modeling/opt_modeling.py

@@ -98,7 +98,9 @@ class OPTLearnedPositionalEmbedding(nn.Module):
         super().__init__()
         self.offset = 2
         self.weight = nn.Parameter(
-            weights.get_tensor(f"{prefix}.decoder.embed_positions.weight")
+            weights.get_tensor(
+                f"{prefix + '.' if prefix else ''}decoder.embed_positions.weight"
+            )
         )
 
     def forward(
@@ -315,7 +317,7 @@ class OPTDecoderLayer(nn.Module):
         super().__init__()
         self.process_group = weights.process_group
         self.hidden_size = config.hidden_size
-        prefix = f"{prefix}.decoder.layers.{layer_id}"
+        prefix = f"{prefix + '.' if prefix else ''}decoder.layers.{layer_id}"
         self.self_attn = OPTAttention(
             config,
             prefix=f"{prefix}.self_attn",
@@ -437,15 +439,17 @@ class OPTDecoder(OPTPreTrainedModel):
         self.max_target_positions = config.max_position_embeddings
         self.vocab_size = config.vocab_size
 
+        prefix = prefix + "." if prefix else ""
+
         self.embed_tokens = TensorParallelEmbedding(
-            prefix=f"{prefix}.decoder.embed_tokens", weights=weights
+            prefix=f"{prefix}decoder.embed_tokens", weights=weights
         )
         self.embed_positions = OPTLearnedPositionalEmbedding(prefix, weights)
 
         if config.word_embed_proj_dim != config.hidden_size:
             self.project_out = FastLinear.load(
                 config,
-                prefix=f"{prefix}.decoder.project_out",
+                prefix=f"{prefix}decoder.project_out",
                 weights=weights,
                 bias=False,
             )
@@ -455,7 +459,7 @@ class OPTDecoder(OPTPreTrainedModel):
         if config.word_embed_proj_dim != config.hidden_size:
             self.project_in = FastLinear.load(
                 config,
-                prefix=f"{prefix}.decoder.project_in",
+                prefix=f"{prefix}decoder.project_in",
                 weights=weights,
                 bias=False,
             )
@@ -467,7 +471,7 @@ class OPTDecoder(OPTPreTrainedModel):
         # see https://github.com/facebookresearch/metaseq/pull/164
         if config.do_layer_norm_before and not config._remove_final_layer_norm:
             self.final_layer_norm = nn.LayerNorm.load(
-                prefix=f"{prefix}.decoder.final_layer_norm", weights=weights, eps=EPS
+                prefix=f"{prefix}decoder.final_layer_norm", weights=weights, eps=EPS
             )
         else:
             self.final_layer_norm = None
@@ -752,15 +756,12 @@ class OPTForCausalLM(OPTPreTrainedModel):
     def __init__(self, prefix, config, weights):
         super().__init__(config)
 
-        if not prefix:
-            prefix = "model"
-        else:
-            prefix = f"{prefix}.model"
-
         self.model = OPTModel(prefix, config, weights)
 
         self.lm_head = SpeculativeHead.load(
-            config, prefix=f"{prefix}.decoder.embed_tokens", weights=weights
+            config,
+            prefix=f"{prefix + '.' if prefix else ''}decoder.embed_tokens",
+            weights=weights,
         )
 
     def forward(