SUPL connection setup

HI Sir/Madam

I downloaded SUPL-C sdk 0.7.2 ad I add the following variable to the prj.conf

#SUPL client library
CONFIG_SUPL_CLIENT_LIB=y
CONFIG_GNSS_SAMPLE_ASSISTANCE_SUPL=y
CONFIG_GNSS_SAMPLE_SUPL_HOSTNAME="supl.google.com"
CONFIG_GNSS_SAMPLE_SUPL_PORT=7276
when I build the program, it reports 
/Users/kevin/Dev/NordicCubee/minicube_main_firmware/prj.conf:34: warning: attempt to assign the value 'y' to the undefined symbol GNSS_SAMPLE_ASSISTANCE_SUPL

/Users/kevin/Dev/NordicCubee/minicube_main_firmware/prj.conf:35: warning: attempt to assign the value '"supl.google.com"' to the undefined symbol GNSS_SAMPLE_SUPL_HOSTNAME

/Users/kevin/Dev/NordicCubee/minicube_main_firmware/prj.conf:36: warning: attempt to assign the value '7276' to the undefined symbol GNSS_SAMPLE_SUPL_PORT

error: Aborting due to Kconfig warnings
I get this variable from the readme file. Please let me know why I can't use this value. Should I use socket to connect SUPL server instead?
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