'Queries the passive column with the provided filter "spec", and
returns a MongoDB cursor.
This should be very fast, as no operation is done (the cursor is only
returned). Next operations (e.g., .count(), enumeration, etc.) might
take a long time, depending on both the operations and the filter.
Any keyword argument is passed to the .find() method of the Mongodb
column object, without any validation (and might have no effect if it
is not expected).'

def get(self, spec, **kargs):

    return self.set_limits(self.find(self.colname_passive, spec, **kargs))
