fixed errors in summary and improved format

balm/succession_diagram.py

@@ -193,6 +193,8 @@ def summary(self) -> str:
                 attrs = self.node_attractor_seeds(node, compute=False)
             except KeyError:
                 continue
+            if not attrs:
+                continue
 
             space = self.node_space(node)
 
@@ -211,7 +213,7 @@ def summary(self) -> str:
                 attr_str = "".join(str(v) for _, v in sorted(attr.items()))
                 report_string += "." * len(space_str_prefix) + f"{attr_str}\n"
             report_string += "\n"
-        return report_string
+        return report_string.rstrip() + "\n"
 
     def root(self) -> int:
         """