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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def decode_bytes(f):
 """Decode a buffer length from a 2-byte unsigned int then read the subsequent bytes. Parameters f: file File-like object with read method. Raises ------ UnderflowDecodeError When the end of stream is encountered before the end of the encoded bytes. Returns ------- int Number of bytes read from `f`. bytes Value bytes decoded from `f`. """


    buf = f.read(FIELD_U16.size)
    if len(buf) < FIELD_U16.size:
        raise UnderflowDecodeError()

    (num_bytes,) = FIELD_U16.unpack_from(buf)
    num_bytes_consumed = FIELD_U16.size + num_bytes

    buf = f.read(num_bytes)
    if len(buf) < num_bytes:
        raise UnderflowDecodeError()

    return num_bytes_consumed, buf