The lookml validator does not raise a warning or error when there is a typo in relationship

[ticastel]

Hello, 

I hope this is the right place to raise this issue. 
As per documentation the syntax for relationship is : 

relationship: one_to_one

When adding this typo : 

relationship: :one_to_one

the lookml validator does not throw any warning or error about it. 
The join seems to work fine but this is an issue when parsing the lookml for other purposes. 

Thanks,