The documentation does not impose any MUST restrictions regarding the use of dots in collection names, only a SHOULD:

Restriction on Collection Names

Collection names should begin with an underscore or a letter character, and cannot:

• contain the $.

• be an empty string (e.g. "").

• contain the null character.

• begin with the system. prefix. (Reserved for internal use.)

• contain .system..

At the same time, the product rejects leading dots and allows trailing dots:

Enterprise test> coll = db['.a']
test..a
Enterprise test> coll.insert({a:1});
Uncaught:
MongoBulkWriteError[InvalidNamespace]: Collection names cannot start with '.': .a

Enterprise test> coll = db['b.'];
test.b.
Enterprise test> coll.insert({a:1});
{
  acknowledged: true,
  insertedIds: { '0': ObjectId('693295b10e96b7c851c76a8c') }
}
Enterprise test> show tables
b.

The python driver however rejects both leading and trailing dots:

        if new_name[0] == "." or new_name[-1] == ".":
            raise InvalidName("collection names must not start or end with '.'")

So which of the three is it? Also, I think validation should only happen in a single location, in the server, and not in the driver.