added nodes time refactor code for issue no. #2766

Author: PalashLalwani

.gitignore

@@ -3,4 +3,6 @@ build-gcc
 python/benchmark/*.trees
 python/benchmark/*.json
 python/benchmark/*.html
+.venv
+.env
 

python/tskit/trees.py

@@ -4561,14 +4561,14 @@ def max_root_time(self):
             raise ValueError(
                 "max_root_time is not defined in a tree sequence with 0 samples"
             )
-        ret = max(self.node(u).time for u in self.samples())
+        ret = max(self.nodes_time[u] for u in self.samples())
         if self.num_edges > 0:
             # Edges are guaranteed to be listed in parent-time order, so we can get the
             # last one to get the oldest root
             edge = self.edge(self.num_edges - 1)
             # However, we can have situations where there is a sample older than a
             # 'proper' root
-            ret = max(ret, self.node(edge.parent).time)
+            ret = max(ret, self.nodes_time[edge.parent])
         return ret
 
     def migrations(self):