Dynamic StoragePath

[RoninX]

Hi guys,
I’m new to Flow but in the docs here, I can see there are certain utility functions which allow you to create a Path.

However, when I try using it inside my smart contract or transaction I get an error as shown in screenshot below:

Does anybody have any idea why this is happening? Does anyone have any sample which I can refer to define dynamic paths in cadence?

[bluesign]

Playground is running on older version of Cadence, you can try on emulator/mainnet/testnet