def serialize_quantity(o):
    """
    Serializes an :obj:`astropy.units.Quantity`, for JSONification.

    Args:
        o (:obj:`astropy.units.Quantity`): :obj:`Quantity` to be serialized.

    Returns:
        A dictionary that can be passed to :obj:`json.dumps`.
    """
    return dict(
        _type='astropy.units.Quantity',
        value=o.value,
        unit=o.unit.to_string())