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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 _get_xapi_session():
    '''
    Get a session to XenAPI. By default, use the local UNIX socket.
    '''
    _xenapi = _check_xenapi()

    xapi_uri = __salt__['config.option']('xapi.uri')
    xapi_login = __salt__['config.option']('xapi.login')
    xapi_password = __salt__['config.option']('xapi.password')

    if not xapi_uri:
        # xend local UNIX socket
        xapi_uri = 'httpu:///var/run/xend/xen-api.sock'
    if not xapi_login:
        xapi_login = ''
    if not xapi_password:
        xapi_password = ''

    try:
        session = _xenapi.Session(xapi_uri)
        session.xenapi.login_with_password(xapi_login, xapi_password)

        yield session.xenapi
    except Exception:
        raise CommandExecutionError('Failed to connect to XenAPI socket.')
    finally:
        session.xenapi.session.logout()