list manipulation - How was Nothing implemented?

How was Nothing implemented in Wolfram language at the language level? For example, {a, b, Nothing, c, d, Nothing} will return {a, b, c, d}. How does Nothing here affect the List? I can't see what mechanism can achieve this effect.

Answer

Ok, I failed to find a duplicate so here is my comment:

I don't know how Nothing is internally implemented but you can do something like this with UpValues:

nothing /: {a___, nothing, b___} := {a, b}

Comments

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