'Sometimes we need to serialize the headers into a more simple form,
a dict for example, in order to send it to msgpack. Since DataTokens
are "complex" classes which msgpack knows nothing about, we need to
replace any of those instances with their value.
:return: None. We\'re modifying self.'

def tokens_to_value(self):

    for (key, val, path, setter) in self.iter_setters():
        if isinstance(val, DataToken):
            setter(val.get_value())
