code: def _raise_error_if_not_sframe(dataset, variable_name="SFrame"):
      
      err_msg = "Input %s is not an SFrame. If it is a Pandas DataFrame,"
      err_msg += " you may use the to_sframe() function to convert it to an SFrame."
  
      if not isinstance(dataset, _SFrame):
        raise ToolkitError(err_msg % variable_name)
docs: Check if the input is an SFrame. Provide a proper error
      message otherwise.