Duck typing

Duck typing is named for "If it walks like a duck and quacks like a duck, it must be a duck."

In programming, it is the attitude that as long as a value/object always behaves like we expect when we interact with it, it doesn't really matter what precise type it actually is.

This is mostly a concept around dynamic typing, where this attitude can save a bunch of keystrokes and text in code that is necessary primarily or only to make the compiler happy.

If this sounds like playing loose, then yes - indeed it can be abused in really fragile and opaque ways.

Or well. Up to you, the programmer.