<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def array2bytes(arr, bytes_type=bytes):
 """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 """

    bio = io.BytesIO()
    np.save(bio, arr, allow_pickle=False)
    return bytes_type(bio.getvalue())