'Scan `search_path` for distributions usable in this environment
Any distributions found are added to the environment.
`search_path` should be a sequence of ``sys.path`` items.  If not
supplied, ``sys.path`` is used.  Only distributions conforming to
the platform/python version defined at initialization are added.'

def scan(self, search_path=None):

    if (search_path is None):
        search_path = sys.path
    for item in search_path:
        for dist in find_distributions(item):
            self.add(dist)
