docs: def get_free_mb(folder):
      """ Return folder/drive free space (in bytes)
      """
      if platform.system() == 'Windows':
          free_bytes = ctypes.c_ulonglong(0)
          ctypes.windll.kernel32.GetDiskFreeSpaceExW(ctypes.c_wchar_p(folder), None, None, ctypes.pointer(free_bytes))
          return free_bytes.value/1024/1024
      else:
          st = os.statvfs(folder)
          return st.f_bavail * st.f_frsize/1024/1024