Return calculator name

    The calculator name is obtained from command option arguments where
    argparse is used. The argument attribute name has to be
    "{calculator}_mode". Then this method returns {calculator}.

def get_interface_mode(args):
    """Return calculator name

    The calculator name is obtained from command option arguments where
    argparse is used. The argument attribute name has to be
    "{calculator}_mode". Then this method returns {calculator}.

    """

    calculator_list = ['wien2k', 'abinit', 'qe', 'elk', 'siesta', 'cp2k',
                       'crystal', 'vasp', 'dftbp', 'turbomole']
    for calculator in calculator_list:
        mode = "%s_mode" % calculator
        if mode in args and args.__dict__[mode]:
            return calculator
    return None