code: def _size_str(size_in_bytes):
      """Returns a human readable size string.
  
      If size_in_bytes is None, then returns "Unknown size".
  
      For example `_size_str(1.5 * tfds.core.units.GiB) == "1.50 GiB"`.
  
      Args:
        size_in_bytes: `int` or `None`, the size, in bytes, that we want to format
          as a human-readable size string.
      """
      if not size_in_bytes:
          return "Unknown size"
  
      size_in_bytes = float(size_in_bytes)
      for name, size_bytes in _NAME_LIST:
          value = size_in_bytes / size_bytes
          if value >= 1.0:
              return "{:.2f} {}".format(value, name)
      return "{} {}".format(int(size_in_bytes), "bytes")
  
label_desc: Use image node_id 1 for calling a global function with example usage: _size_str(size_in_bytes) and returns: str, str, str