@staticmethod
def p_block(symbols):
    """block : SPACE block
                 | line ENDOFLINE
                 | line_error ENDOFLINE
                 | chorus ENDOFLINE
                 | tab ENDOFLINE
                 | bridge ENDOFLINE
                 | ENDOFLINE
        """
    if len(symbols) == 3 and isinstance(symbols[1], str):
        symbols[0] = symbols[2]
    elif symbols[1] is None or len(symbols) == 2:
        symbols[0] = None
    else:
        symbols[0] = symbols[1]
