Change HashMap to BTreeMap.

Cargo.toml

@@ -40,7 +40,7 @@ internals = []                  # expose internal data structures
 unicode-xid-ident = ["unicode-xid"] # allow Unicode Standard Annex #31 for identifiers.
 metadata = ["serde", "serde_json"]  # enables exporting functions metadata to JSON
 
-no_std = ["smallvec/union", "num-traits/libm", "hashbrown", "core-error", "libm", "ahash/compile-time-rng"]
+no_std = ["smallvec/union", "num-traits/libm", "core-error", "libm", "ahash/compile-time-rng"]
 
 # compiling for WASM
 wasm-bindgen = ["instant/wasm-bindgen"]
@@ -63,12 +63,6 @@ default_features = false
 features = ["alloc"]
 optional = true
 
-[dependencies.hashbrown]
-version = "0.11"
-default-features = false
-features = ["ahash", "nightly", "inline-more"]
-optional = true
-
 [dependencies.serde]
 version = "1.0"
 default_features = false