Filter and sort associative array

[Head Scratcher via Digitalmars-d-learn]

I am just learning D. So far, I am impressed by its elegance and 
power.

I have an associative array bool[string]. I want to filter it by 
value (!bool), then extract the keys and sort them. I am 
struggling with the syntax and working with ranges. I can't find 
any documentation related to filtering associative arrays.

This is what I currently have, but it doesn't compile:

auto sortedStrings = myAssocArray.byKeyValue.filter!((string 
k,value) => !value).assocArray.keys.sort();