def apply_multiplicities(data):
    """
    Takes in the Data class of scattering data returned by convert_to_numpy()
    and applies the multiplicity to each intensity.

    Sets the multiplicity to 1 to avoid accidental double-use.
    Parameters
    ----------
    data : Data

    Returns
    -------
    data: Data
        Updated with multiplicities

    """
    for i in range(len(data.tth)):
        data.I[i] *= data.mult[i]
        data.mult[i] = 1
    return data