No export option in Unity

[Username98978787]

Unity 2019 and 2017 has the following error when the script is imported

[NegInfinity]

WeightedMode is not part of Unity 2017 api and Unity 2017 is not supported. The type is built into the engine.
https://docs.unity3d.com/ScriptReference/WeightedMode.html

Unity 2019.2 and 2018.4.18 on my end do not produce this error. If the error persists please upload a minimal project which triggers it so I can take a look at it.