def __add__(self, other):
        """Add an environment or distribution to an environment"""
        new = self.__class__([], platform=None, python=None)
        for env in self, other:
            new += env
        return new
Add an environment or distribution to an environment
stackoverflow/venv/lib/python3.6/site-packages/pip-19.0.3-py3.6.egg/pip/_vendor/pkg_resources/__init__.py