How to change uci named section to unnamed?

Question

I have config file on openwrt platform. Config file contains named sections and I need to delete name from section that it become unnamed section.

Example

config core 'main'
    option session_timeout '1800'
    option lang 'en'
    option firstlogin '0'
    option advanced '1'

And I need to change to

config core
    option session_timeout '1800'
    option lang 'en'
    option firstlogin '0'
    option advanced '1'

I'm not able to that with uci. Did I miss something?