Remove unused imports

compiler/router/bbox_node.py

@@ -3,8 +3,6 @@
 # Copyright (c) 2016-2023 Regents of the University of California, Santa Cruz
 # All rights reserved.
 #
-from .bbox import bbox
-
 
 class bbox_node:
     """

compiler/router/graph.py

@@ -7,7 +7,6 @@ import heapq
 from copy import deepcopy
 from openram import debug
 from openram.base.vector import vector
-from openram.base.vector3d import vector3d
 from openram.tech import drc
 from .bbox import bbox
 from .bbox_node import bbox_node

compiler/router/graph_shape.py

@@ -5,7 +5,6 @@
 #
 from openram.base.pin_layout import pin_layout
 from openram.base.vector import vector
-from openram.tech import drc
 from .graph_utils import snap