def determine_platform():
    """ Untility function to return the platform currenlty in use.

    Returns
    ---------
    pf: str
        'darwin' (MacOS), 'debian'(debian Linux) or 'win' (windows)
    """
    import platform
    pform = platform.platform().lower()
    if 'darwin' in pform:
        pf = 'darwin'
    elif 'debian' in pform:
        pf = 'debian'
    elif 'ubuntu' in pform:
        pf = 'debian'
    elif 'win' in pform:
        pf = 'win'
    else:
        raise ValueError('Not able to find out the platform.')
    return pf
