Update `internal` function in library contracts

[0x0918]

Explanation of internal function in library contracts.

What type of PR is this (这是什么类型的PR)

• [ ✅] Typo(勘误)

Which issue(s) this PR fixes(Optional) (这个PR 修复了什么问题 (可选择))

• resolve(修复) : # add explanation of internal function call instructions in library contracts.