How to refer to user created filter value?

[tumikosha]

If the  user creates filter for a column
I can check it with `_is_filtered` 
but how I can insert value from this filter? Because I do not know the name of the filter,  just field name

  derived_table: {
    sql:   select
          …….
   where              
                  {% if explore.field._is_filtered %}                         
                        and field=  {????? value for filtering expression???}
                   {% endif %}

Especially, how to do  that with date filters?