How to use the soupsieve.css_parser.CSSParser function in soupsieve

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
    )

# CSS pattern for `:indeterminate`
CSS_INDETERMINATE = CSSParser(
    '''
    html|input[type="checkbox"][indeterminate],
    html|input[type="radio"]:is(:not([name]), [name=""]):not([checked]),
    html|progress:not([value]),

    /*
    This pattern must be at the end.
    Special logic is applied to the last selector.
    */
    html|input[type="radio"][name][name!='']:not([checked])
    '''
).process_selectors(flags=FLG_PSEUDO | FLG_HTML | FLG_INDETERMINATE)
# CSS pattern for `:disabled`
CSS_DISABLED = CSSParser(
    '''
    html|*:is(input[type!=hidden], button, select, textarea, fieldset, optgroup, option, fieldset)[disabled],
    html|optgroup[disabled] > html|option,
    html|fieldset[disabled] > html|*:is(input[type!=hidden], button, select, textarea, fieldset),
    html|fieldset[disabled] >
        html|*:not(legend:nth-of-type(1)) html|*:is(input[type!=hidden], button, select, textarea, fieldset)
    '''
).process_selectors(flags=FLG_PSEUDO | FLG_HTML)
# CSS pattern for `:enabled`
CSS_ENABLED = CSSParser(
    '''
    html|*:is(input[type!=hidden], button, select, textarea, fieldset, optgroup, option, fieldset):not(:disabled)
    '''
).process_selectors(flags=FLG_PSEUDO | FLG_HTML)
# CSS pattern for `:required`
CSS_REQUIRED = CSSParser(

'''
    html|*:is(input[type!=hidden], button, select, textarea, fieldset, optgroup, option, fieldset)[disabled],
    html|optgroup[disabled] > html|option,
    html|fieldset[disabled] > html|*:is(input[type!=hidden], button, select, textarea, fieldset),
    html|fieldset[disabled] >
        html|*:not(legend:nth-of-type(1)) html|*:is(input[type!=hidden], button, select, textarea, fieldset)
    '''
).process_selectors(flags=FLG_PSEUDO | FLG_HTML)
# CSS pattern for `:enabled`
CSS_ENABLED = CSSParser(
    '''
    html|*:is(input[type!=hidden], button, select, textarea, fieldset, optgroup, option, fieldset):not(:disabled)
    '''
).process_selectors(flags=FLG_PSEUDO | FLG_HTML)
# CSS pattern for `:required`
CSS_REQUIRED = CSSParser(
    'html|*:is(input, textarea, select)[required]'
).process_selectors(flags=FLG_PSEUDO | FLG_HTML)
# CSS pattern for `:optional`
CSS_OPTIONAL = CSSParser(
    'html|*:is(input, textarea, select):not([required])'
).process_selectors(flags=FLG_PSEUDO | FLG_HTML)
# CSS pattern for `:placeholder-shown`
CSS_PLACEHOLDER_SHOWN = CSSParser(
    '''
    html|input:is(
        :not([type]),
        [type=""],
        [type=text],
        [type=search],
        [type=url],
        [type=tel],

msg = "Invalid character {!r} position {}".format(c, index)
                raise SelectorSyntaxError(msg, self.pattern, index)
        if self.debug:  # pragma: no cover
            print('## END PARSING')

    def process_selectors(self, index=0, flags=0):
        """Process selectors."""

        return self.parse_selectors(self.selector_iter(self.pattern), index, flags)


# Precompile CSS selector lists for pseudo-classes (additional logic may be required beyond the pattern)
# A few patterns are order dependent as they use patterns previous compiled.

# CSS pattern for `:link` and `:any-link`
CSS_LINK = CSSParser(
    'html|*:is(a, area, link)[href]'
).process_selectors(flags=FLG_PSEUDO | FLG_HTML)
# CSS pattern for `:checked`
CSS_CHECKED = CSSParser(
    '''
    html|*:is(input[type=checkbox], input[type=radio])[checked], html|option[selected]
    '''
).process_selectors(flags=FLG_PSEUDO | FLG_HTML)
# CSS pattern for `:default` (must compile CSS_CHECKED first)
CSS_DEFAULT = CSSParser(
    '''
    :checked,

    /*
    This pattern must be at the end.
    Special logic is applied to the last selector.