code: def array2bytes(arr, bytes_type=bytes):
      
      bio = io.BytesIO()
      np.save(bio, arr, allow_pickle=False)
      return bytes_type(bio.getvalue())
docs: Wraps NumPy's save function to return bytes.
  
      We use :func:`numpy.save` rather than :meth:`numpy.ndarray.tobytes` because
      it encodes endianness and order.
  
      Args:
          arr (:obj:`numpy.ndarray`):
              Array to be saved.
  
          bytes_type (class, optional, default=bytes):
              This class will be used to wrap the bytes objects in the
              serialization if `use_bytes` is true. Useful for when using
              Python 2 and using BSON encoding, which will not accept the raw
              `bytes` type, so `bson.Binary` can be used instead.
  
  
      Returns:
          bytes_type