code: def getsize(path, bestprefix=True, system=NIST):
      
      _path = os.path.realpath(path)
      size_bytes = os.path.getsize(_path)
      if bestprefix:
          return Byte(size_bytes).best_prefix(system=system)
      else:
          return Byte(size_bytes)
docs: Return a bitmath instance in the best human-readable representation
  of the file size at `path`. Optionally, provide a preferred unit
  system by setting `system` to either `bitmath.NIST` (default) or
  `bitmath.SI`.
  
  Optionally, set ``bestprefix`` to ``False`` to get ``bitmath.Byte``
  instances back.