Migrating to MongoDB: how to query GROUP BY + WHERE

I have a MYSQL table with records of people's names and the time of arrival expresed as a number. Think of it as a marathon. I want to know how many people arrived into a certain gap of time who where named the same, so:

SELECT name, COUNT(*) FROM mydb.mytable
WHERE Time>=100 AND Time<=1000
GROUP BY name

And as results I get:

Susan, 1
John, 4
Frederick, 1
Paul, 2

I'm migrating to MongoDB now, and using Python to code (so I'm asking for Pymongo help). I tried looking for information about the GROUP BY equivalent (even when I have read that NoSQL databases are worse at this kind of operation than the SQL ones), but since they released the new agreggate API, I hjaven't been able to find a simple example like this solved with the group method, the Map-Reduce method or the brand new agreggate API.

Any help?