public Frame copy() {
    return new Frame(locals.copy(), stack.copy(), subroutines);
  }
Makes and returns a mutable copy of this instance. The copy contains copies of the locals and
stack (that is, it doesn't share them with the original).

@return {@code non-null;} the copy
android/android_framework/dex-maker/src/main/java/com/android/dx/cf/code/Frame.java