"    Input:  {
               Input for 'filter' function

               (aggregation) - dict with some params
                               (keys_start) - prune keys
                               (keys_end)   - prune keys
            }

    Output: {
              return       - return code =  0, if successful
                                         >  0, if error
              (error)      - error text if return > 0

              all_meta     - each key is a list with all values
              all_tags     - each key is a tag with a number of occurances
            }

"