Query().apply_custom_filter method needs to be improved

Query().apply_custom_filter does simple exact search for custom filters. This does not server the purpose most of the time ( at least for me ) . I need to filter using mongodb operators like $regex, $ne , $ge etc which is ignored by this method. This method is used by semantic_query method which , which results in filter filtering everything out. If we are filtering the text result from semantic query, we should be able to support the mongodb operators like $regex, $eq etc. We could use library like pymongoquery to support mongo operator like filtering from our results without making a trip to the mongo databse.

Start with Query().apply_custom_filter and its use from semantic_query; inspect how custom filters are applied to semantic-query results. Compare the current behavior with the MongoDB operators named in the issue, including $regex, $ne, $ge, and $eq. Done means these operators filter results correctly without making another trip to MongoDB.

Written by the indexing model from the issue text.