parameters: (expr, lh_arg, rh_arg)
docstring: Helper function to combine arguments.
docstring_summary: Helper function to combine arguments.
docstring_tokens: Helper function to combine arguments .
function: def join(expr, lh_arg, rh_arg):
      """Helper function to combine arguments.
      """
      if lh_arg is None or rh_arg is None:
          return None
      else:
          return expr.copy([lh_arg, rh_arg])
function_tokens: def join ( expr , lh_arg , rh_arg ) : if lh_arg is None or rh_arg is None : return None else : return expr . copy ( [ lh_arg , rh_arg ] )