code: def device_type_from_string(cl_device_type_str):
      
      cl_device_type_str = cl_device_type_str.upper()
      if hasattr(cl.device_type, cl_device_type_str):
          return getattr(cl.device_type, cl_device_type_str)
      return None
docs: Converts values like ``gpu`` to a pyopencl device type string.
  
      Supported values are: ``accelerator``, ``cpu``, ``custom``, ``gpu``. If ``all`` is given, None is returned.
  
      Args:
          cl_device_type_str (str): The string we want to convert to a device type.
  
      Returns:
          cl.device_type: the pyopencl device type.