Check that the data value is fixed width bytes,
    matching the schema['size'] exactly!

    Parameters
    ----------
    datum: Any
        Data being validated
    schema: dict
        Schema
    kwargs: Any
        Unused kwargs

def validate_fixed(datum, schema, **kwargs):
    """
    Check that the data value is fixed width bytes,
    matching the schema['size'] exactly!

    Parameters
    ----------
    datum: Any
        Data being validated
    schema: dict
        Schema
    kwargs: Any
        Unused kwargs
    """
    return (
            (isinstance(datum, bytes) and len(datum) == schema['size'])
            or (isinstance(datum, decimal.Decimal))
    )