code: def p_generate_if_woelse(self, p):
          'generate_if : IF LPAREN cond RPAREN gif_true_item'
          p[0] = IfStatement(p[3], p[5], None, lineno=p.lineno(1))
          p.set_lineno(0, p.lineno(1)f p_generate_if_woelse(self, p):
          'generate_if : IF LPAREN cond RPAREN gif_true_item'
          p[0] = IfStatement(p[3], p[5], None, lineno=p.lineno(1))
          p.set_lineno(0, p.lineno(1))
docs: generate_if : IF LPAREN cond RPAREN gif_true_item