Dictionaries in BAML have this syntax. You’ll see them mainly in tests declared in BAML, and clients.

BAML
1{
2 key1 value1
3 key2 {
4 nestedKey1 nestedValue1
5 }
6}

Note they do not use :

You can use unquoted or quoted strings, booleans, numbers and nested dictionaries as values.

BAML
1{
2 key1 "value1"
3 key2 {
4 nestedKey1 1
5 nestedKey2 true
6 }
7}

Dictionary with multiline string as a value:

BAML
1{
2 key1 #"
3 This is a
4 multiline string
5 "#
6}