feat: support external custom models (#13429)

Co-authored-by: qiuxuan.lzw <qiuxuan.lzw@alibaba-inc.com>
Co-authored-by: Mick <mickjagger19@icloud.com>

test/srt/test_external_models.py

@@ -0,0 +1,28 @@
+import os
+import unittest
+
+import sglang as sgl
+from sglang.test.test_utils import CustomTestCase
+
+
+class TestExternalModels(CustomTestCase):
+    def test_external_model(self):
+        os.environ["SGLANG_EXTERNAL_MODEL_PACKAGE"] = "external_models"
+        os.environ["SGLANG_EXTERNAL_MM_PROCESSOR_PACKAGE"] = "external_models"
+        prompt = "Today is a sunny day and I like"
+        model_path = "Qwen/Qwen2-VL-2B-Instruct"
+
+        engine = sgl.Engine(
+            model_path=model_path,
+            cuda_graph_max_bs=1,
+            max_total_tokens=64,
+            enable_multimodal=True,
+        )
+        out = engine.generate(prompt)["text"]
+        engine.shutdown()
+
+        self.assertGreater(len(out), 0)
+
+
+if __name__ == "__main__":
+    unittest.main()