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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 recoverPubkey(idText, cert, caPubkey):
 """ A client can recover the server's pubkey using the identity string @idText, server's implicit @cert, and the trusted @caPubkey. """

    # Verify types
    assertType(cert, ec1Element)
    assertType(caPubkey, ec1Element)

    # Compute the pubkey
    return _exp(cert, idText)*cert + caPubkey