code: def _expr2code(self, arg_list, expr):
          
          code = lambdastr(arg_list, expr)
          function_code = code.split(':')[1].strip()
          #for arg in arg_list:
          #    function_code = function_code.replace(arg.name, 'self.'+arg.name)
  
          return function_code
docs: Convert the given symbolic expression into code.