Merges two dictionaries of values recursively. This is a very naive
        implementation that expects the two dictionaries to be fairly similar 
        in structure.

        @param to_values destination dictionary
        @param from_values dictionary with values to copy

def _merge_values(self, to_values, from_values):
        """Merges two dictionaries of values recursively. This is a very naive
        implementation that expects the two dictionaries to be fairly similar 
        in structure.

        @param to_values destination dictionary
        @param from_values dictionary with values to copy
        """
        if from_values is not None:
            for k, v in from_values.items():
                if k in to_values and isinstance(to_values[k], dict):
                    self._merge_values(to_values[k], v) # merge
                else:
                    to_values[k] = v # replaces instead of merge
        return to_values