def get_replacements_list(self, format_string):
        """
        If possible, returns a list of filtered placeholders in ``format_string``.
        """
        replacements = getattr(self._py3status_module, "replacements", None)
        if not replacements or not format_string:
            return []

        if format_string not in self._format_placeholders:
            placeholders = self._formatter.get_placeholders(format_string)
            self._format_placeholders[format_string] = placeholders
        else:
            placeholders = self._format_placeholders[format_string]

        # filter placeholders
        found = set()
        for replacement in replacements:
            for placeholder in placeholders:
                if placeholder == replacement:
                    found.add(placeholder)
        return list(found or placeholders)

        If possible, returns a list of filtered placeholders in ``format_string``.
        
py3status/py3.py