code: 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)
docs: 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.