import struct


def _Unpack(content, offset, format_string):
  """Unpack the content at the offset.

  Args:
    content: String to be unpacked.
    offset: Offset from the beginning of the content.
    format_string: Format string of struct module.
  Returns:
    See struct.unpack.
  """
  size = struct.calcsize(format_string)
  result = struct.unpack(format_string, content[offset : offset + size])
  return result