def format_symbolic_duration(symbolic_dur):
    """Create a string representation of the symbolic duration encoded
    in the dictionary `symbolic_dur`.

    Parameters
    ----------
    symbolic_dur : dict
        Dictionary with keys 'type' and 'dots'

    Returns
    -------
    str
        A string representation of the specified symbolic duration

    Examples
    --------
    >>> format_symbolic_duration({'type': 'q', 'dots': 2})
    'q..'

    >>> format_symbolic_duration({'type': '16th'})
    '16th'

    """
    if symbolic_dur is None:

        return "unknown"

    else:
        result = (symbolic_dur.get("type") or "") + "." * symbolic_dur.get("dots", 0)

        if "actual_notes" in symbolic_dur and "normal_notes" in symbolic_dur:

            result += "_{}/{}".format(
                symbolic_dur["actual_notes"], symbolic_dur["normal_notes"]
            )

        return result