Does this line starts a new markdown cell?
        Then, return the cell marker

def start_of_new_markdown_cell(self, line):
        """Does this line starts a new markdown cell?
        Then, return the cell marker"""
        for empty_markdown_cell in ['""', "''"]:
            if line == empty_markdown_cell:
                return empty_markdown_cell

        for triple_quote in ['"""', "'''"]:
            if line.startswith(triple_quote):
                return triple_quote

        if self.twenty_hash.match(line):
            return line

        return None