decapitalize
Returns a copy of this string having its first letter lowercased using the rules of the default locale, or the original string if it's empty or already starts with a lower case letter.
import java.util.Locale
import kotlin.test.*
fun main(args: Array<String>) {
//sampleStart
println("abcd".decapitalize()) // abcd
println("Abcd".decapitalize()) // abcd
//sampleEnd
}