Make ClientvLLM.model_name a cached_property (#862)

* Update `ClientvLLM.model_name` to `cached_property`

* Fix unit test

src/distilabel/llms/vllm.py

@@ -13,6 +13,7 @@
 # limitations under the License.
 
 import json
+from functools import cached_property
 from typing import (
     TYPE_CHECKING,
     Any,
@@ -497,8 +498,8 @@ def load(self) -> None:
             self.tokenizer, revision=self.tokenizer_revision
         )
 
-    @property
-    def model_name(self) -> str:
+    @cached_property
+    def model_name(self) -> str:  # type: ignore
         """Returns the name of the model served with vLLM server."""
         models = self._client.models.list()
         return models.data[0].id

tests/unit/llms/test_vllm.py

@@ -179,15 +179,14 @@ def test_prepare_batches_and_sort_back(
 @mock.patch("openai.AsyncOpenAI")
 class TestClientvLLM:
     def test_clientvllm_model_name(
-        self, _openai_mock: mock.MagicMock, _async_openai_mock: mock.MagicMock
+        self, _: mock.MagicMock, openai_mock: mock.MagicMock
     ) -> None:
         llm = ClientvLLM(
             base_url="http://localhost:8000/v1",
             tokenizer="google-bert/bert-base-uncased",
         )
 
-        llm.load()
-
+        llm._client = mock.MagicMock()
         llm._client.models.list.return_value = SyncPage[Model](  # type: ignore
             data=[Model(id="llama", created=1234, object="model", owned_by="")],
             object="model",