protected function consumeHeadline($lines, $current)
	{
		$line = trim($lines[$current]);
		$level = 1;
		while (isset($line[$level]) && $line[$level] === '=' && $level < 6) {
			$level++;
		}
		$block = [
			'headline',
			// parse headline content. The leading and trailing '='s are removed.
			'content' => $this->parseInline(trim($line, " \t=")),
			'level' => $level,
		];
		return [$block, $current];
	}