Assuming that there are three devices in the inventory, what is wrong with the following YAML data?

inventory:

csr$1$kv$1$: ios$-$xe

csr$1$kv$2$: nx$-$os

csr$1$kv$3$: ios$-$xe

Everything looks correct.

The line csr$1$kv$2$: nx$-$os cannot have nx$-$os as a value.

The indentation is invalid.

The text $-$ sign$$ is absent at the beginning of each line.