### test value of symbolic expression's operator

I need to define a boolean function is_pow that takes for argument a symbolic expression expr
an that return True if and only if expr.operator is the builtin function pow.
But I don'n know which the syntax to use:

Of course

def is_pow(expr):
return expr.operator() == <built-in function pow>

doesn't work. Has someone the answer ?
Thanks a lot.