Init obj_dict in Common, and use super()

Give the Common class an `__init__() that sets up the `obj_dict`,
and call `super().__init__` from all of the subclasses. Makes the
code in the subclass `__init__`s simpler.

src/pydot/core.py

@@ -553,6 +553,9 @@ class Common:
     this one.
     """
 
+    def __init__(self, obj_dict: Optional[AttributeDict] = None) -> None:
+        self.obj_dict: AttributeDict = obj_dict or {}
+
     def __getstate__(self) -> AttributeDict:
         _dict = copy.copy(self.obj_dict)
         return _dict
@@ -668,18 +671,8 @@ def __init__(
         obj_dict: Optional[AttributeDict] = None,
         **attrs: Any,
     ) -> None:
-        #
-        # Nodes will take attributes of
-        # all other types because the defaults
-        # for any GraphViz object are dealt with
-        # as if they were Node definitions
-        #
-        if obj_dict is not None:
-            self.obj_dict = obj_dict
-
-        else:
-            self.obj_dict = {}
-
+        super().__init__(obj_dict)
+        if obj_dict is None:
             # Copy the attributes
             #
             self.obj_dict["attributes"] = dict(attrs)
@@ -783,21 +776,18 @@ def __init__(
         obj_dict: Optional[AttributeDict] = None,
         **attrs: Any,
     ) -> None:
-        self.obj_dict = {}
-        if isinstance(src, (Node, Subgraph, Cluster)):
-            src = src.get_name()
-        if isinstance(dst, (Node, Subgraph, Cluster)):
-            dst = dst.get_name()
-        points = (src, dst)
-        self.obj_dict["points"] = points
+        super().__init__(obj_dict)
         if obj_dict is None:
-            # Copy the attributes
+            if isinstance(src, (Node, Subgraph, Cluster)):
+                src = src.get_name()
+            if isinstance(dst, (Node, Subgraph, Cluster)):
+                dst = dst.get_name()
+            points = (src, dst)
+            self.obj_dict["points"] = points
             self.obj_dict["attributes"] = dict(attrs)
             self.obj_dict["type"] = "edge"
             self.obj_dict["parent_graph"] = None
             self.obj_dict["sequence"] = None
-        else:
-            self.obj_dict = obj_dict
 
     def __str__(self) -> str:
         return self.to_string()
@@ -964,12 +954,8 @@ def __init__(
         simplify: bool = False,
         **attrs: Any,
     ) -> None:
-        if obj_dict is not None:
-            self.obj_dict = obj_dict
-
-        else:
-            self.obj_dict = {}
-
+        super().__init__(obj_dict)
+        if obj_dict is None:
             self.obj_dict["attributes"] = dict(attrs)
 
             if graph_type not in ["graph", "digraph"]:
@@ -1549,15 +1535,13 @@ def __init__(
         simplify: bool = False,
         **attrs: Any,
     ) -> None:
-        Graph.__init__(
-            self,
+        super().__init__(
             graph_name=graph_name,
             obj_dict=obj_dict,
             suppress_disconnected=suppress_disconnected,
             simplify=simplify,
             **attrs,
         )
-
         if obj_dict is None:
             self.obj_dict["type"] = "subgraph"
 
@@ -1602,15 +1586,13 @@ def __init__(
         simplify: bool = False,
         **attrs: Any,
     ) -> None:
-        Graph.__init__(
-            self,
+        super().__init__(
             graph_name=graph_name,
             obj_dict=obj_dict,
             suppress_disconnected=suppress_disconnected,
             simplify=simplify,
             **attrs,
         )
-
         if obj_dict is None:
             self.obj_dict["type"] = "subgraph"
             self.obj_dict["name"] = quote_id_if_necessary(
@@ -1629,8 +1611,8 @@ class Dot(Graph):
     the base class 'Graph'.
     """
 
-    def __init__(self, *argsl: Any, **argsd: Any) -> None:
-        Graph.__init__(self, *argsl, **argsd)
+    def __init__(self, *args: Any, **kwargs: Any) -> None:
+        super().__init__(*args, **kwargs)
 
         self.shape_files: List[str] = []
         self.formats = OUTPUT_FORMATS