docs: def load_plugins(self):
          """Load plugins from entry point(s)."""
          from pkg_resources import iter_entry_points
          seen = set()
          for entry_point in self.entry_points:
              for ep in iter_entry_points(entry_point):
                  if ep.name in seen:
                      continue
                  seen.add(ep.name)
                  try:
                      plugincls = ep.load()
                  except Exception as exc:
                      # never let a plugin load kill us
                      warn("Unable to load plugin %s: %s" % (ep, exc),
                           RuntimeWarning)
                      continue
                  plugin = plugincls()
                  self.add_plugin(plugin)
          super(EntryPointPluginManager, self).load_plugins()