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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 format_contains(self, format_string, names):
 """ Determines if ``format_string`` contains a placeholder string ``names`` or a list of placeholders ``names``. ``names`` is tested against placeholders using fnmatch so the following patterns can be used: .. code-block:: none * 	 matches everything ? 	 matches any single character [seq] 	matches any character in seq [!seq] 	matches any character not in seq This is useful because a simple test like ``'{placeholder}' in format_string`` will fail if the format string contains placeholder formatting eg ``'{placeholder:.2f}'`` """

        # We cache things to prevent parsing the format_string more than needed
        if isinstance(names, list):
            key = str(names)
        else:
            key = names
            names = [names]
        try:
            return self._format_placeholders_cache[format_string][key]
        except KeyError:
            pass

        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]

        if format_string not in self._format_placeholders_cache:
            self._format_placeholders_cache[format_string] = {}

        for name in names:
            for placeholder in placeholders:
                if fnmatch(placeholder, name):
                    self._format_placeholders_cache[format_string][key] = True
                    return True
        self._format_placeholders_cache[format_string][key] = False
        return False