Implemented support for pickle

Closes #13

.vscode/settings.json

@@ -1,4 +1,4 @@
 {
     "esbonio.sphinx.confDir": "${workspaceFolder}\\docs",
-    "workbench.colorTheme": "Default Dark+"
+    "workbench.colorTheme": "Default Dark Modern"
 }

multiformats/cid/__init__.py

@@ -225,6 +225,9 @@ def __new__(cls: Type[_CIDSubclass],
             return CID._new_instance(cls, base, version, codec, hashfun, digest)
         return CID._new_instance(cls, base, version, codec, hashfun, (hashfun, raw_digest))
 
+    def __getnewargs__(self) -> tuple[Multibase, CIDVersion, Multicodec, bytes]:
+        return self.base, self.version, self.codec, self.digest
+
     @staticmethod
     def _new_instance(CID_subclass: Type[_CIDSubclass],
                       base: Multibase,

multiformats/multiaddr/__init__.py

@@ -86,6 +86,9 @@ def __new__(cls, codec: Union[str, int, Multicodec]) -> "Proto":
         _cache[codec.name] = instance
         return instance
 
+    def __getnewargs__(self) -> tuple[Multicodec]:
+        return (self.codec,)
+
     @property
     def name(self) -> str:
         """

multiformats/multibase/__init__.py

@@ -89,6 +89,9 @@ def __new__(cls,
         instance._description = description
         return instance
 
+    def __getnewargs__(self) -> tuple[str, str, MultibaseStatus, str]:
+        return (self.name, self.code, self.status, self.description)
+
     @staticmethod
     def _validate_name(name: Optional[str]) -> str:
         validate(name, Optional[str])

multiformats/multicodec/__init__.py

@@ -96,6 +96,9 @@ def __new__(cls,
         instance._description = description
         return instance
 
+    def __getnewargs__(self) -> tuple[str, str, int, MulticodecStatus, str]:
+        return (self.name, self.tag, self.code, self.status, self.description)
+
     @staticmethod
     def _validate_name(name: str) -> str:
         if not re.match(r"^[a-z][a-z0-9_-]+$", name):

multiformats/multihash/__init__.py

@@ -83,6 +83,9 @@ def __new__(cls, codec: Union[str, int, Multicodec]) -> "Multihash":
         _cache[codec.name] = instance
         return instance
 
+    def __getnewargs__(self) -> tuple[Multicodec]:
+        return (self.codec,)
+
     @property
     def name(self) -> str:
         """