def to_nested_dict(row):
    result = {}
    for key, value in row._mapping.items():
        keys = key.split('.')
        current_level = result
        for part in keys[:-1]:
            if part not in current_level:
                current_level[part] = {}
            current_level = current_level[part]
        current_level[keys[-1]] = value
    return result