Function dict_depth 

pub fn dict_depth<K, V>(d: &HashMap<K, V>) -> usize
where
    K: Hash + Eq,

Get the nesting depth of a nested HashMap

Example

use polyglot_sql::helper::dict_depth;
use std::collections::HashMap;

let empty: HashMap<String, ()> = HashMap::new();
assert_eq!(dict_depth(&empty), 1);

let mut nested: HashMap<String, HashMap<String, ()>> = HashMap::new();
nested.insert("a".into(), HashMap::new());
// Note: This returns 1 because we can't traverse into nested hashmaps generically