Provider part

Future<String> updateInstitution(
      final String institutionId, final Asset file) async {
    final String filePath = await file.filePath;
    dev.log(filePath, name: "Ulan", sequenceNumber: 15, zone: Zone.root);
    final MultipartFile multipartFile = await MultipartFile.fromPath('photo', filePath, filename: file.name, contentType: MediaType("image", "jpg"),);
    print(multipartFile.filename);
    final document = ''' 
    mutation update(\$postBackgound: Upload!){ addDataInstitution(token:"",  institutionId: $institutionId imageBackground: \$postBackgound ){
        imageBackgroundUrl
      }
    }
   ''';
   dev.log(document, name: "WTF", zone: Zone.root);
   dev.log(multipartFile.filename);
   print('ohhh');
    final QueryResult result = await GraphqlConnection.connection().mutate(
      MutationOptions(
        document: document,
        variables: {
          'postBackgound': multipartFile
        },
        fetchPolicy: FetchPolicy.networkOnly
      ),
    );
    print(result.data);
    print(result.errors);
  }