models/package: move `requires()` and `version` to `DistPackage` (#295)

src/pipdeptree/_models/package.py

@@ -81,13 +81,6 @@ class Package(ABC):
             fr = FrozenRequirement.from_dist(our_dist, [])  # type: ignore[call-arg]
         return str(fr).strip()
 
-    def requires(self) -> list[Requirement]:
-        return self._obj.requires()  # type: ignore[no-untyped-call,no-any-return]
-
-    @property
-    def version(self) -> str:
-        return self._obj.version  # type: ignore[no-any-return]
-
     def __repr__(self) -> str:
         return f'<{self.__class__.__name__}("{self.key}")>'
 
@@ -108,6 +101,13 @@ class DistPackage(Package):
         super().__init__(obj)
         self.req = req
 
+    def requires(self) -> list[Requirement]:
+        return self._obj.requires()  # type: ignore[no-untyped-call,no-any-return]
+
+    @property
+    def version(self) -> str:
+        return self._obj.version  # type: ignore[no-any-return]
+
     def render_as_root(self, *, frozen: bool) -> str:
         if not frozen:
             return f"{self.project_name}=={self.version}"