sort method
{"name" : "x" , "age" : 15} ,
{"name" : "y" , "age" : 20} , {"name" : "z" , "age" : 25}
sort("age" , Sorting.ascending) => (first element) {"name" : "x" , "age" : 15}
Implementation
void sort(String fieldName, Sorting sorting) {
_sorts[fieldName] = sorting;
}