from datetime import datetime


def format_unixnano(unixnano):
    """Formats an integer unix timestamp from nanoseconds to a user readable
    string

    Args:
        unixnano (int): integer unix timestamp in nanoseconds
    Returns:
        formatted_time (str)
    """
    return datetime.fromtimestamp(int(unixnano / 1e6) / 1000.0)\
        .strftime('%Y-%m-%d %H:%M:%S.%f')