* and stop setting default values in python operator code, so defaults can be set at the server side.

This issue is just for the PR and questions from maintainers. 
setup.py
"""
    Compile and build the frontend assets using yarn and webpack.
    Registered as cmdclass in setup() so it can be called with ``python setup.py compile_assets``.
    """
    description = "Compile and build the frontend assets"
    user_options: List[str] = []
    def initialize_options(self) -> None:
        """Set default values for options."""
    def finalize_options(self) -> None:
        """Set final values for options."""
    def run(self) -> None:
        """Run a command to compile and build assets."""
        subprocess.check_call('./airflow/www/compile_assets.sh')
class ListExtras(Command):
    """
    List all available extras
    Registered as cmdclass in setup() so it can be called with ``python setup.py list_extras``.
    """
    description = "List available extras"
    user_options: List[str] = []
    def initialize_options(self) -> None:
        """Set default values for options."""
    def finalize_options(self) -> None:
        """Set final values for options."""
    def run(self) -> None:
        """List extras."""
        print("\n".join(wrap(", ".join(EXTRAS_REQUIREMENTS.keys()), 100)))
def git_version(version_: str) -> str: