refactor nodes into standalone file

backend/nodes/coordinate_pair.py

@@ -0,0 +1,25 @@
+from __future__ import annotations
+from backend.node_registry import register_node
+
+
+@register_node(display_name="Coordinate Pair")
+class CoordinatePair:
+    """Provide a pair of Coordinates, for drawing lines between markers, etc."""
+
+    @classmethod
+    def INPUT_TYPES(cls):
+        return {
+            "required": {
+                "a": ("COORD",),
+                "b": ("COORD",),
+            }
+        }
+
+    RETURN_TYPES = ("COORDPAIR",)
+    RETURN_NAMES = ("coord pair",)
+    FUNCTION = "process"
+
+    DESCRIPTION = "Output a pair of coordinates."
+
+    def process(self, a: tuple, b: tuple) -> tuple:
+        return ((a, b),)