如何创建具有私有过程的Oracle包？

CREATE OR REPLACE PACKAGE package_name IS
  PROCEDURE public_procedure1;
  PROCEDURE public_procedure2;
  FUNCTION public_function1 RETURN NUMBER;
  FUNCTION public_function2 RETURN VARCHAR2;
END package_name;
/

CREATE OR REPLACE PACKAGE BODY package_name IS
  PROCEDURE public_procedure1 IS
  BEGIN
    -- 实现公共过程1的代码
  END;

  PROCEDURE public_procedure2 IS
  BEGIN
    -- 实现公共过程2的代码
  END;

  FUNCTION public_function1 RETURN NUMBER IS
    -- 实现公共函数1的代码
  BEGIN
    RETURN 0;
  END;

  FUNCTION public_function2 RETURN VARCHAR2 IS
    -- 实现公共函数2的代码
  BEGIN
    RETURN 'Hello';
  END;

  PROCEDURE private_procedure IS
  BEGIN
    -- 实现私有过程的代码
  END;
END package_name;
/

BEGIN
  package_name.public_procedure1;
  package_name.public_procedure2;
  dbms_output.put_line(package_name.public_function1);
  dbms_output.put_line(package_name.public_function2);
  -- 无法直接调用 private_procedure
END;