When using a lazy reversed sequence: ```ts const rev = Seq([10, 11, 12]) .filter(() => true) // make this seq lazy .reverse(); ``` The keys of this sequence is set to "NaN" when using either "__iterate" or "__iterator" Example : https://immutable-js.com/play/#WwogIC4uLlNlcShbMTAsIDExLCAxMl0pCiAgICAuZmlsdGVyKCgpID0+IHRydWUpIC8vIG1ha2UgdGhpcyBzZXEgbGF6eQogICAgLnJldmVyc2UoKQogICAgLnRvS2V5ZWRTZXEoKQogICAgLnJldmVyc2UoKS5lbnRyaWVzKCkKXQ== https://immutable-js.com/play/#U2VxKFsxMCwgMTEsIDEyXSkKICAgICAgLmZpbHRlcigoKSA9PiB0cnVlKSAvLyBtYWtlIHRoaXMgc2VxIGxhenkKICAgICAgLnJldmVyc2UoKQogICAgICAucmVkdWNlUmlnaHQoCiAgICAgICAgKGFjYywgdmFsdWUsIGtleSkgPT4gewogICAgICAgICAgYWNjLnB1c2goW2tleSwgdmFsdWVdKTsKCiAgICAgICAgICByZXR1cm4gYWNjOwogICAgICAgIH0sCiAgICAgICAgW10KICAgICAgKTs=
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