code: func (e *baseError) StackFrames() []StackFrame {
  	e.framesOnce.Do(func() {
  		e.stackFrames = make([]StackFrame, len(e.stack))
  		for i, pc := range e.stack {
  			frame := &e.stackFrames[i]
  			frame.PC = pc
  			frame.Func = runtime.FuncForPC(pc)
  			if frame.Func != nil {
  				frame.FuncName = frame.Func.Name()
  				frame.File, frame.LineNumber = frame.Func.FileLine(frame.PC - 1)
  			}
  		}
  	})
  	return e.stackFrames
  }
docs: // Implements DropboxError interface.