presto-main/src/main/java/io/prestosql/operator/scalar/StringFunctions.java/StringFunctions/trim
class StringFunctions:    @Description("removes whitespace from the beginning and end of a string")
    @ScalarFunction
    @LiteralParameters("x")
    @SqlType("varchar(x)")
    public static Slice trim(@SqlType("varchar(x)") Slice slice)
    {
        return SliceUtf8.trim(slice);
    }