ElasticSearch : Is it possible to loop with mustache in a ElasticSearchTemplate

In an ElasticSearch Template , I would like to to that :

  "aggs": {
        "att_characteristic": {
          "filters": {
            "filters": {
              
              "" : {"term": { "characteristic.code": ""}}, 
              
            }
          },
          "aggs": {
            "agg_by_value": {
              "terms": {
                "field": "characteristic.value",
                "size": 10000
              },
              "aggs": {
                "top_reverse_nested": {
                  "reverse_nested": {}
                }
              }
            }
          }
        }
      }

But I am getting the following error:

   "reason" : "Improperly closed variable in query-template:1 @[query-template:1]"

It bugs at :

  "" : {"term": { "characteristic.code": ""}}, 

Can we loop in an ElasticSearch Template with Mustache language as in another language?

PS : It is called with

GET index-name-dev/_search/template
{
  "id": "search-template-test",
  "params": {
    "agg-att":[{"code":"Color"},
               {"code":"Shape"},
               {"code":"Size"}]
  }
}

Thanks !

UPDATE : Here below is a full example

The mapping is the following :

PUT tly-idx_test1
{
  "mappings": {
    "properties": {
      "fieldA": {
        "type": "keyword"
      },
      "fieldArrayA": {
        "type": "keyword"
      },
     "fieldArrayB": {
      "type": "nested",
      "properties": {
        "color": {
          "type": "keyword",
          "fields": {
            "text": {
              "type": "text",
              "analyzer": "standard"
              }
            }
          },
          "size": {
            "type": "keyword",
            "fields": {
              "text": {
                "type": "text",
                "analyzer": "standard"
                }
              }
          },
          "shape": {
            "type": "keyword",
            "fields": {
              "text": {
                "type": "text",
                "analyzer": "standard"
                }
              }
            },
          "value": {
            "type": "keyword",
            "fields": {
              "text": {
                "type": "text",
                "analyzer": "standard"
                }
              }
            },
          "obligatoire": {
            "type": "boolean"
            }
        }
     },
      "fieldB": {
        "type": "text"
      },
      "fieldC": {
        "type": "text"
      },
      "fieldD": {
        "type": "text"
      },
      "fieldE": {
        "type": "boolean"
      }
    }
  }
}

Here below is some data to put in the test index

POST tly-idx_test1/_doc
{
  "fieldA": "M",
  "fieldB": "SHOWER PACK",
  "fieldC": "false",
  "fieldD": "01",
  "fieldE": "true",
  "fieldArrayA": [
    "val1",
    "val2",
    "val3"
  ],
   "fieldArrayB": [
    {"color":"red","size":"10cm","shape":"square","obligatoire":true,"value":"15"},
    {"color":"blue","size":"100cm","shape":"circle","obligatoire":true ,"value":"25"},
    {"color":"green","size":"50cm","shape":"rectangle","obligatoire":true ,"value":"35"},
    {"color":"yellow","size":"22cm","shape":"triangle","obligatoire":true ,"value":"45"}
    
  ]
}

Here below is the template

GET tly-idx_test1/_search
{
  "query": {
    "match_all": {}
  },
  "aggregations": {
    "agg-attributs": {
      "nested": {
        "path": "fieldArrayB"
      },
      "aggs": {
        "att_obligatoire": {
          "filters": {
            "filters": {
              
              "" : {"term": { "fieldArrayB.color": ""}}, 
              
            }
          },
          "aggs": {
            "agg_by_value": {
              "terms": {
                "field": "fieldArrayB.value",
                "size": 10000
              },
              "aggs": {
                "top_reverse_nested": {
                  "reverse_nested": {}
                }
              }
            }
          }
        }
      }
    }
  }
}

Finally, here below is the template calling :

GET tly-idx_test1/_search/template
{
  "id": "tly-template-test",
  "params": {
    "agg-att": [{"code": "color"},
                {"code": "shape"},
                {"code": "size","last": true}
    ]
  }
}

I got the same error

"reason" : "Improperly closed variable in query-template:1 @[query-template:1]"

Why does the loop does not work?