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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def _extract_sel_info(sel):
 """Recurse down parsed tree, return pseudo class info"""

    from cssselect2.parser import (CombinedSelector, CompoundSelector,
                                   PseudoClassSelector,
                                   FunctionalPseudoClassSelector)
    steps = []
    extras = []
    if isinstance(sel, CombinedSelector):
        lstep, lextras = _extract_sel_info(sel.left)
        rstep, rextras = _extract_sel_info(sel.right)
        steps = lstep + rstep
        extras = lextras + rextras
    elif isinstance(sel, CompoundSelector):
        for ssel in sel.simple_selectors:
            s, e = _extract_sel_info(ssel)
            steps.extend(s)
            extras.extend(e)
    elif isinstance(sel, FunctionalPseudoClassSelector):
        if sel.name == 'pass':
            steps.append(serialize(sel.arguments).strip('"\''))
    elif isinstance(sel, PseudoClassSelector):
        if sel.name == 'deferred':
            extras.append('deferred')
    return (steps, extras)