No longer overwrites manual bonds (#232)

* No longer overwrites manual bonds

No longer overwrites bonds that were added manually before the atoms object was sent to ZnDraw

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* different approach using hasattr

* typing error

* whitespace error

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

---------

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

zndraw/zndraw.py

@@ -155,7 +155,9 @@ def on_size(size):
     def _set_item(self, index, value):
         assert isinstance(value, ase.Atoms), "Must be an ASE Atoms object"
         assert isinstance(index, int), "Index must be an integer"
-        if self.bonds_calculator is not None:
+        if hasattr(value, "connectivity"):
+            pass
+        elif self.bonds_calculator is not None:
             value.connectivity = self.bonds_calculator.build_graph(value)
         else:
             value.connectivity = nx.Graph()