code: def p_levelsigs_comma(self, p):
          'levelsigs : levelsigs COMMA levelsig'
          p[0] = p[1] + (p[3],)
          p.set_lineno(0, p.lineno(1)f p_levelsigs_comma(self, p):
          'levelsigs : levelsigs COMMA levelsig'
          p[0] = p[1] + (p[3],)
          p.set_lineno(0, p.lineno(1))
docs: levelsigs : levelsigs COMMA levelsig