JSON Query errors in Pipelines - null and other issues

HI

I also use Make Request tonnes of time , glad to see someone else using it. 

For boolean , I am able to pass entry via true or false

      "{{ a.body_params.iproof_send_fid }}": {"value": "{{true}}"},

For Handling Null , I actually have been using condition so far

  {% if inner_key is defined and element is defined %}
or 
{% if a.body_params.caption %}

But it's great to see the to_json option to handle this , can you explain what else it does?