Remove _node_edges and _tree_node_edges

Fixes #2359

Author: hyanwong

python/tskit/trees.py

@@ -2438,18 +2438,6 @@ def nodes(self, root=None, order="preorder"):
         root = -1 if root is None else root
         return iterator(root)
 
-    def _node_edges(self):
-        """
-        Return a numpy array mapping the node IDs in this tree to the ID of the edge
-        above them. This is in lieu of a tree.edge(u) function, currently implemented
-        using the non-optimised Python TreeSequence._tree_node_edges() generator
-        """
-        for index, node_edge_map in enumerate(  # pragma: no branch
-            self.tree_sequence._tree_node_edges()
-        ):
-            if index == self.index:
-                return node_edge_map
-
     def _as_newick_fast(self, *, root, precision, legacy_ms_labels):
         """
         Call into the fast but limited C implementation of the newick conversion.
@@ -5394,20 +5382,6 @@ def edge(self, id_):
             metadata_decoder=self.table_metadata_schemas.edge.decode_row,
         )
 
-    def _tree_node_edges(self):
-        """
-        Return a generator over the trees in the tree sequence, yielding a numpy array
-        that maps the node IDs in the tree to the ID of the edge above them.
-        Currently this is a private, non-optimised Python implementation.
-        """
-        node_edges = np.full(self.num_nodes, NULL, dtype=np.int32)
-        for _, edges_out, edges_in in self.edge_diffs():
-            for e in edges_out:
-                node_edges[e.child] = NULL
-            for e in edges_in:
-                node_edges[e.child] = e.id
-            yield node_edges
-
     def migration(self, id_):
         """
         Returns the :ref:`migration <sec_migration_table_definition>` in this tree