def _add_data(source, target):
    """Add data from source to target dict. Both dicts must have two keys.

    Args:
        source: Source dict
        target: Target dict

    Returns:
        target: Aggregated data

    """
    # Process data
    for primary in source.keys():
        for secondary, value in source[primary].items():
            target[primary][secondary] = value

        # Return
    return target