To support pip install for model_training package. (#3643)

For the Python module: model_training, the original package management
file pyproject.toml was configured with "py-modules =
["model_training"]". However, "py-modules" is typically used for setting
up single file modules, not for Python packages. The original
configuration could possibly cause "pip install ." to fail to install
model_training in the Python environment (only
model_training-1.0.0.dist-info is available under
/usr/local/lib/python/).

model/pyproject.toml

@@ -42,7 +42,7 @@ tests = [
 ]
 
 [tool.setuptools]
-py-modules = ["model_training"]
+packages = ["model_training"]
 
 [tool.black]
 line-length = 120