Does the RAM power-down library support nRF9160?

Hello everyone.

I am developing a custom board using the nRF9160. I tried using the RAM power-down library based on the Power optimization recommendations page of the nRF Connect SDK.

CONFIG_RAM_POWER_DOWN_LIBRARY=y 

However, when building I got the following message:

warning: RAM_POWER_DOWN_LIBRARY (defined at C:/ncs/v2.6.1/nrf\lib\ram_pwrdn/Kconfig:7) was assigned
the value 'y' but got the value 'n'. Check these unsatisfied dependencies: (SOC_NRF52840 ||
SOC_NRF52833 || SOC_NRF5340_CPUAPP) (=n). See
http://docs.zephyrproject.org/latest/kconfig.html#CONFIG_RAM_POWER_DOWN_LIBRARY and/or look up
RAM_POWER_DOWN_LIBRARY in the menuconfig/guiconfig interface. The Application Development Primer,
Setting Configuration Values, and Kconfig - Tips and Best Practices sections of the manual might be
helpful too.

It seems that the RAM power down library does not support nRF9160, so please tell me how to use the RAM power down library with the nRF9160. 
Thanks in advance.
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