Frame.caller constructor
- int level = 1
Returns a single frame of the current stack.
By default, this will return the frame above the current method. If
level is 0, it will return the current method's frame; if level is
higher than 1, it will return higher frames.
Implementation
factory Frame.caller([int level = 1]) {
  if (level < 0) {
    throw ArgumentError('Argument [level] must be greater than or equal '
        'to 0.');
  }
  return Trace.current(level + 1).frames.first;
}