def merge(self, destination, source):
        """
        run me with nosetests --with-doctest file.py

        >>> a = { 'first' : { 'all_rows' : { 'pass' : 'dog', 'number' : '1' } } }
        >>> b = { 'first' : { 'all_rows' : { 'fail' : 'cat', 'number' : '5' } } }
        >>> merge(a, b) == { 'first' : { 'all_rows' : { 'pass' : 'dog', 'fail' : 'cat', 'number' : '5' } } }
        """
        if isinstance(source, dict):
            for key, value in source.items():
                if isinstance(value, dict):
                    # get node or create one
                    node = destination.setdefault(key, {})
                    if node is not None:
                        self.merge(node, value)
                    else:
                        destination[key] = value
                else:
                    destination[key] = value