prevent unnecessary network calls so that aipg works when offline

Signed-off-by: Markus Schuettler <markus.schuettler@tngtech.com>

service/comfyui_downloader.py

@@ -121,6 +121,14 @@ def _install_pip_requirements(requirements_txt_path: str):
 
 
 def install_pypi_package(packageSpecifier: str):
+    installed_packages = aipg_utils.call_subprocess(f"{service_config.comfyui_python_exe} -m pip list")
+    if packageSpecifier.endswith(".whl"):
+        package_name = packageSpecifier.split("/")[-1].split("-")[0]
+    else:
+        package_name = packageSpecifier.split("==")[0]
+    if package_name in installed_packages:
+        logging.info(f"package {package_name} already installed. Omitting installation")
+        return
     if packageSpecifier.endswith(".whl"):
         pip_specifier = os.path.abspath(os.path.join(service_config.comfyui_python_env, packageSpecifier.split("/")[-1]))
         try: