Dot not allowed in key names

I am trying to import an existing database into mongo.

The keys in the database don't contain the period character, but a lot of the lists in the documents themselves do.
So I am getting a lot of errors like this:

pymongo.errors.InvalidName: key 'web2.0' must not contain '.'

Is it strictly necessary to prohibit dots in the keys?
Is there a convenient workaround?