code: def selectapi(api):
      
      global __SELECTED_API, USED_API
      if api.lower() not in {"pyqt4", "pyqt5", "pyside", "pyside2"}:
          raise ValueError(api)
  
      if __SELECTED_API is not None and __SELECTED_API.lower() != api.lower():
          raise RuntimeError("A Qt API {} was already selected"
                             .format(__SELECTED_API))
      elif __SELECTED_API is None:
          __SELECTED_API = api.lower()
          from . import _api
          USED_API = _api.USED_API
docs: Select an Qt API to use.
  
      This can only be set once and before any of the Qt modules are explicitly
      imported.