def extract_units(tokens, start, result):
    """Extract units from bracketed after nu"""
    for e in result:
        for child in e.iter():
            if 'cm−1' in child.text:
                return [E('units', 'cm−1')]
    return []
def extract_units ( tokens , start , result ) : for e in result : for child in e . iter ( ) : if 'cm−1' in child . text : return [ E ( 'units' , 'cm−1' ) ] return [ ]
Extract units from bracketed after nu