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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 kdf(size, password, salt, opslimit=OPSLIMIT_SENSITIVE, memlimit=MEMLIMIT_SENSITIVE, encoder=nacl.encoding.RawEncoder):
 """ Derive a ``size`` bytes long key from a caller-supplied ``password`` and ``salt`` pair using the argon2i memory-hard construct. the enclosing module provides the constants - :py:const:`.OPSLIMIT_INTERACTIVE` - :py:const:`.MEMLIMIT_INTERACTIVE` - :py:const:`.OPSLIMIT_MODERATE` - :py:const:`.MEMLIMIT_MODERATE` - :py:const:`.OPSLIMIT_SENSITIVE` - :py:const:`.MEMLIMIT_SENSITIVE` as a guidance for correct settings. :param size: derived key size, must be between :py:const:`.BYTES_MIN` and :py:const:`.BYTES_MAX` :type size: int :param password: password used to seed the key derivation procedure; it length must be between :py:const:`.PASSWD_MIN` and :py:const:`.PASSWD_MAX` :type password: bytes :param salt: **RANDOM** salt used in the key derivation procedure; its length must be exactly :py:const:`.SALTBYTES` :type salt: bytes :param opslimit: the time component (operation count) of the key derivation procedure's computational cost; it must be between :py:const:`.OPSLIMIT_MIN` and :py:const:`.OPSLIMIT_MAX` :type opslimit: int :param memlimit: the memory occupation component of the key derivation procedure's computational cost; it must be between :py:const:`.MEMLIMIT_MIN` and :py:const:`.MEMLIMIT_MAX` :type memlimit: int :rtype: bytes .. versionadded:: 1.2 """


    return encoder.encode(
        nacl.bindings.crypto_pwhash_alg(size, password, salt,
                                        opslimit, memlimit,
                                        ALG)
    )