Modifies the given dict into a flat dict consisting of only
        key/value pairs.

def _flatten_dict(self, dict_):
        """Modifies the given dict into a flat dict consisting of only
        key/value pairs.
        """
        flattened_dict = {}
        for (key, value) in dict_.iteritems():
            if isinstance(value, dict):
                flattened_dict.update(self._flatten_dict(value))
            else:
                flattened_dict[key] = value
        return flattened_dict