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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 _cached_css_compile(pattern, namespaces, custom, flags):
 """Cached CSS compile."""


    custom_selectors = process_custom(custom)
    return cm.SoupSieve(
        pattern,
        CSSParser(pattern, custom=custom_selectors, flags=flags).process_selectors(),
        namespaces,
        custom,
        flags
    )