Force only 1 llama-cpp-python version at a time for now

Author: oobabooga

Diff for: modules/llama_cpp_python_hijack.py

@@ -7,30 +7,47 @@
 from modules.cache_utils import process_llamacpp_cache
 
 
+imported_module = None
+
+
 def llama_cpp_lib():
+    global imported_module
+
     return_lib = None
 
     if shared.args.cpu:
+        if imported_module and imported_module != 'llama_cpp':
+            raise Exception(f"Cannot import 'llama_cpp' because '{imported_module}' is already imported. See issue #1575 in llama-cpp-python. Please restart the server before attempting to use a different version of llama-cpp-python.")
         try:
             return_lib = importlib.import_module('llama_cpp')
+            imported_module = 'llama_cpp'
         except:
             pass
 
     if shared.args.tensorcores and return_lib is None:
+        if imported_module and imported_module != 'llama_cpp_cuda_tensorcores':
+            raise Exception(f"Cannot import 'llama_cpp_cuda_tensorcores' because '{imported_module}' is already imported. See issue #1575 in llama-cpp-python. Please restart the server before attempting to use a different version of llama-cpp-python.")
         try:
             return_lib = importlib.import_module('llama_cpp_cuda_tensorcores')
+            imported_module = 'llama_cpp_cuda_tensorcores'
         except:
             pass
 
     if return_lib is None:
+        if imported_module and imported_module != 'llama_cpp_cuda':
+            raise Exception(f"Cannot import 'llama_cpp_cuda' because '{imported_module}' is already imported. See issue #1575 in llama-cpp-python. Please restart the server before attempting to use a different version of llama-cpp-python.")
         try:
             return_lib = importlib.import_module('llama_cpp_cuda')
+            imported_module = 'llama_cpp_cuda'
         except:
             pass
 
     if return_lib is None and not shared.args.cpu:
+        if imported_module and imported_module != 'llama_cpp':
+            raise Exception(f"Cannot import 'llama_cpp' because '{imported_module}' is already imported. See issue #1575 in llama-cpp-python. Please restart the server before attempting to use a different version of llama-cpp-python.")
         try:
             return_lib = importlib.import_module('llama_cpp')
+            imported_module = 'llama_cpp'
         except:
             pass