trimMargin 
  Trims leading whitespace characters followed by marginPrefix from every line of a source string and removes the first and the last lines if they are blank (notice difference blank vs empty).
Doesn't affect a line if it doesn't contain marginPrefix except the first and the last blank lines.
Doesn't preserve the original line endings.
Since Kotlin
1.0Parameters
marginPrefix 
non-blank string, which is used as a margin delimiter. Default is | (pipe character).
See also
Samples
import java.util.Locale
import kotlin.test.*
fun main() { 
   //sampleStart 
   val withoutMargin1 = """ABC
123
456""".trimMargin()
println(withoutMargin1) // ABC\n123\n456
val withoutMargin2 = """
    #XYZ
    #foo
    #bar
""".trimMargin("#")
println(withoutMargin2) // XYZ\nfoo\nbar 
   //sampleEnd
}