Is ChangePasswordAsync for ASP .Net Core 3.1 available on GitHub?

This is related to .NET Core 3.1 ChangePasswordAsync Inner Exception “Cannot update Identity column”

I am attempting to understand how ChangePasswordAsync works and was looking for it on Github. I found an archived version from an older version of Identity that is now locked. But, I prefer to have the current version in order to identify any potential breaking change. Does anyone know where the current development copy of it is?

https://docs.microsoft.com/en-us/dotnet/api/microsoft.aspnetcore.identity.usermanager-1.changepasswordasync?view=aspnetcore-3.1

Any help is appreciated it.