https://freemarker.apache.org/: FreeMarker is a "template engine"; a generic tool to generate text output based on templates. (Apache Software Foundation) 
class freemarker.core.BuiltInsForHashes
  minor version: 0
  major version: 59
  flags: flags: (0x0020) ACC_SUPER
  this_class: freemarker.core.BuiltInsForHashes
  super_class: java.lang.Object
{
  private void <init>();
    descriptor: ()V
    flags: (0x0002) ACC_PRIVATE
    Code:
      stack=1, locals=1, args_size=1
        start local 0 // freemarker.core.BuiltInsForHashes this
         0: .line 56
            aload 0 /* this */
            invokespecial java.lang.Object.<init>:()V
            return
        end local 0 // freemarker.core.BuiltInsForHashes this
      LocalVariableTable:
        Start  End  Slot  Name  Signature
            0    1     0  this  Lfreemarker/core/BuiltInsForHashes;
}
SourceFile: "BuiltInsForHashes.java"
NestMembers:
  freemarker.core.BuiltInsForHashes$keysBI  freemarker.core.BuiltInsForHashes$valuesBI
InnerClasses:
  keysBI = freemarker.core.BuiltInsForHashes$keysBI of freemarker.core.BuiltInsForHashes
  valuesBI = freemarker.core.BuiltInsForHashes$valuesBI of freemarker.core.BuiltInsForHashes