Stage must be a properly formatted document - warning

Hi,
for this snippet
{
from: ‘comments’,
let: {‘id’: ‘$_id’},
pipeline: [
{"$match":
{"$expr": {"$eq": ["$movie_id", “$$id”]}}}
}
],
as: ‘movie_comments’
}

in Compas aggregation bulder I get warning thet it is not properly formatted. I cannot see any problems. Maybe a pair of fresh eyes could help. Thank you.

The line

has too many closing braces.

Thank you. That’s it.