code: def add(modname, features, required_version, installed_version=None,
          optional=False):
      
      global DEPENDENCIES
      for dependency in DEPENDENCIES:
          if dependency.modname == modname:
              raise ValueError("Dependency has already been registered: %s"\
                               % modname)
      DEPENDENCIES += [Dependency(modname, features, required_version,
                                  installed_version, optional)]
docs: Add Spyder dependency