code: def where(self, code):
          
          self.__check_okay_to_chain()
          if not isinstance(code, Code):
              code = Code(code)
  
          self.__spec["$where"] = code
          return self
docs: Adds a $where clause to this query.
  
          The `code` argument must be an instance of :class:`basestring`
          (:class:`str` in python 3) or :class:`~bson.code.Code`
          containing a JavaScript expression. This expression will be
          evaluated for each document scanned. Only those documents
          for which the expression evaluates to *true* will be returned
          as results. The keyword *this* refers to the object currently
          being scanned.
  
          Raises :class:`TypeError` if `code` is not an instance of
          :class:`basestring` (:class:`str` in python 3). Raises
          :class:`~pymongo.errors.InvalidOperation` if this
          :class:`Cursor` has already been used. Only the last call to
          :meth:`where` applied to a :class:`Cursor` has any effect.
  
          :Parameters:
            - `code`: JavaScript expression to use as a filter