Checks if a package is installed using an installable flag '-e' without use of pip's internal API

is_development_install.py

def is_development_install(package: str) -> bool:
    """Check if we're running a development installation"""
    import pkg_resources
    file = Path(dirname(pkg_resources.__file__)).parent
    file = file.joinpath(package.replace('_', '-') + '.egg-link')
    return file.exists()