{{alias}}( [dtype] )
    Returns the single letter character abbreviation for a specified underlying
    array data type.

    If not provided a data type value, the function returns an object mapping
    data type strings to single letter character abbreviations.

    If provided an unknown/unsupported data type, the function returns `null`.

    Parameters
    ----------
    dtype: any (optional)
        Data type value.

    Returns
    -------
    ch: Object|string|null
        Single letter character abbreviation(s).

    Examples
    --------
    > var ch = {{alias}}( 'float64' )
    'd'
    > ch = {{alias}}( 'foobar' )
    null
    > var obj = {{alias}}()
    {...}

    See Also
    --------