def xidz(numerator, denominator, value_if_denom_is_zero):
    """
    Implements Vensim's XIDZ function.
    This function executes a division, robust to denominator being zero.
    In the case of zero denominator, the final argument is returned.

    Parameters
    ----------
    numerator: float
    denominator: float
        Components of the division operation
    value_if_denom_is_zero: float
        The value to return if the denominator is zero

    Returns
    -------
    numerator / denominator if denominator > 1e-6
    otherwise, returns value_if_denom_is_zero
    """
    small = 1e-6  # What is considered zero according to Vensim Help
    if abs(denominator) < small:
        return value_if_denom_is_zero
    else:
        return numerator * 1.0 / denominator