parameters: (self)
docstring: List the variables used (read or written) by the instruction.
docstring_summary: List the variables used (read or written) by the instruction.
docstring_tokens: List the variables used ( read or written ) by the instruction .
function: def list_vars(self):
          """
          List the variables used (read or written) by the instruction.
          """
          raise NotImplementedError
function_tokens: def list_vars ( self ) : raise NotImplementedError