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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 encrypt(key, pt, Nk=4):
 """Encrypt a plain text block."""

    assert Nk in {4, 6, 8}
    rkey = key_expand(key, Nk)
    ct = cipher(rkey, pt, Nk)

    return ct