Add helper method to retrieve declared type (#18)

* Add helper function to retrieve declared type

* Use helper in HierarkeyProxy

hierarkey/models.py

@@ -63,6 +63,14 @@ def add_default(self, key: str, value: Optional[str], default_type: type = str)
         """
         self.defaults[key] = HierarkeyDefault(value, default_type)
 
+    def get_declared_type(self, key: str) -> type:
+        """
+        Returns the type that is declared for a key using add_default.
+
+        :param key: Key
+        """
+        return self.defaults[key].type if key in self.defaults else None
+
     def add_type(self, type: type, serialize: Callable[[Any], str], unserialize: Callable[[str], Any]) -> None:
         """
         Adds serialization support for a new type.

hierarkey/proxy.py

@@ -156,8 +156,8 @@ def get(self, key: str, default=None, as_type: type = None, binary_file: bool =
         If you receive a ``File`` object, it will already be opened. You can specify the ``binary_file``
         flag to indicate that it should be opened in binary mode.
         """
-        if as_type is None and key in self._h.defaults:
-            as_type = self._h.defaults[key].type
+        if as_type is None:
+            as_type = self._h.get_declared_type(key)
 
         if key in self._cache():
             value = self._cache()[key]