
ext_modules: Python modules are either "pure" modules, containing only Python code, or "extension" modules written in the low-level language of the Python implementation. Here we are listing the extension modules in the build, including the main torch._C library that contains our Python Tensor
cmdclass: When using the setup.py script from the command line, the user must specify one or more "commands", code snippets that perform a specific action. For example, the "install" command builds and installs the package. This mapping routes specific commands to functions in setup.py that implement them
packages: The list of packages in the project. These are "pure" - i.e. they only contain Python code. These are defined elsewhere in setup.py
package_data: Additional files that need to be installed into a package: in this case the header files and shared libraries that the build will generate must be included in our installation
