human
I wrote the below code

    node = ast.parse(s, mode=u'eval')
    def _eval(node):
        if isinstance(node, ast.Expression):
            return _eval(node.body)
        elif isinstance(node, ast.Str):
            return node.s
        elif isinstance(node, ast.Num):
            return node.n
        elif isinstance(node, ast.BinOp):
            return _binOps[type(node.op)](_eval(node.left), _eval(node.right))
        else:
            raise Exception(u'Unsupported    type    {0}'.format(node))
    return _eval(node.body)

What's a good function header?
 ... Here's a good function header?
assistant
#Here's a good function header.

def arithmeticEval(s):