code: def downloads_per_year(collection, code, raw=False):
      
  
      tc = ThriftClient()
  
      body = {"query": {"filtered": {}}}
  
      fltr = {}
  
      query = {
          "query": {
              "bool": {
                  "must": [
                      {
                          "match": {
                              "collection": collection
                          }
                      }
                  ]
              }
          }
      }
  
      aggs = {
          "aggs": {
              "access_year": {
                  "terms": {
                      "field": "access_year",
                      "size": 0,
                      "order": {
                          "_term": "asc"
                      }
                  },
                  "aggs": {
                      "access_total": {
                          "sum": {
                              "field": "access_total"
                          }
                      }
                  }
              }
          }
      }
  
      body['query']['filtered'].update(fltr)
      body['query']['filtered'].update(query)
      body.update(aggs)
  
      code_type = _code_type(code)
  
      if code_type:
          query["query"]["bool"]["must"].append({
              "match": {
                  code_type: code
              }
          })
  
      query_parameters = [
          ('size', '0')
      ]
  
      query_result = tc.search(json.dumps(body), query_parameters)
  
      return query_result if raw is True else _compute_downloads_per_year(query_result)
docs: This method retrieve the total of downloads per year.
  
      arguments
      collection: SciELO 3 letters Acronym
      code: (Journal ISSN, Issue PID, Article PID)
  
      return
      [
          ("2017", "20101"),
          ("2016", "11201"),
          ("2015", "12311"),
          ...
      ]