[Bug fix] Anthropic, Llama2 and VertexAI LLMs dependencies (#820)

embedchain/llm/vertex_ai.py

@@ -1,3 +1,4 @@
+import importlib
 import logging
 from typing import Optional
 
@@ -5,6 +6,14 @@ from embedchain.config import BaseLlmConfig
 from embedchain.helper.json_serializable import register_deserializable
 from embedchain.llm.base import BaseLlm
 
+try:
+    importlib.import_module("vertexai")
+except ModuleNotFoundError:
+    raise ModuleNotFoundError(
+        "The required dependencies for VertexAI are not installed."
+        'Please install with `pip install --upgrade "embedchain[vertexai]"`'
+    ) from None
+
 
 @register_deserializable
 class VertexAILlm(BaseLlm):