def flat_prior(value, boundaries=[None, None]):
    """
    Set up a flat prior on a paramater.
    Out of the bounds, the prior return 0, else it returns 1.
    
    Parameters
    ----------
    value : [float]
        The paramater to apply the prior on.
    
    boundaries : [list[float]]
        Boundaries of the flat prior.
    
    
    Returns
    -------
    float
    """
    if boundaries[0] is not None and value < boundaries[0]:
        return 0
    if boundaries[1] is not None and value > boundaries[1]:
        return 0
    return 1
