code: def p_expr_require_once(p):
      'expr : REQUIRE_ONCE expr'
      p[0] = ast.Require(p[2], True, lineno=p.lineno(1)f p_expr_require_once(p):
      'expr : REQUIRE_ONCE expr'
      p[0] = ast.Require(p[2], True, lineno=p.lineno(1))
docs: expr : REQUIRE_ONCE expr