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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 set_default_keychain(keychain, domain="user", user=None):
    '''
    Set the default keychain

    keychain
        The location of the keychain to set as default

    domain
        The domain to use valid values are user|system|common|dynamic, the default is user

    user
        The user to set the default keychain as

    CLI Example:

    .. code-block:: bash

        salt '*' keychain.set_keychain /Users/fred/Library/Keychains/login.keychain
    '''
    cmd = "security default-keychain -d {0} -s {1}".format(domain, keychain)
    return __salt__['cmd.run'](cmd, runas=user)