Update crates and added methods to get a key or all keys in an IndexMap

Cargo.toml

@@ -7,9 +7,9 @@ edition = "2021"
 approx = { version = "0.5.1", optional = true }
 
 [dev-dependencies]
-plotters = { version = "0.3.1", default-features = false, features = ["svg_backend", "all_elements", "all_series"] }
+plotters = { version = "0.3.4", default-features = false, features = ["svg_backend", "all_elements", "all_series"] }
-plotters-backend = "0.3.2"
+plotters-backend = "0.3.4"
-time = { version = "0.3.9", features = ["parsing"] }
+time = { version = "0.3.17", features = ["parsing"] }
 trueskill-tt = { path = ".", features = ["approx"] }
 
 [profile.release]

src/lib.rs

@@ -77,6 +77,17 @@ where
             idx
         }
     }
+
+    pub fn key(&self, idx: Index) -> Option<&K> {
+        self.0
+            .iter()
+            .find(|(_, &value)| value == idx)
+            .map(|(key, _)| key)
+    }
+
+    pub fn keys(&self) -> impl Iterator<Item = &K> {
+        self.0.keys()
+    }
 }
 
 impl<K> Default for IndexMap<K>