Pulls values off the request in the provided location
        :param request: The flask request object to parse arguments from

def source(self, request):
        """Pulls values off the request in the provided location
        :param request: The flask request object to parse arguments from
        """
        if isinstance(self.location, six.string_types):
            value = getattr(request, self.location, MultiDict())
            if callable(value):
                value = value()
            if value is not None:
                return value
        else:
            values = MultiDict()
            for l in self.location:
                value = getattr(request, l, None)
                if callable(value):
                    value = value()
                if value is not None:
                    values.update(value)
            return values

        return MultiDict()