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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 randombytes(size):
 """ Returns ``size`` number of random bytes from a cryptographically secure random source. :param size: int :rtype: bytes """

    buf = ffi.new("unsigned char[]", size)
    lib.randombytes(buf, size)
    return ffi.buffer(buf, size)[:]