code: def _add_zero_flow_controls_at_boundary(
      control_point_locations: TensorLike,
      control_point_flows: TensorLike,
      image_height: TensorLike,
      image_width: TensorLike,
      boundary_points_per_edge: TensorLike,
  ) -> tf.Tensor:
      """Add control points for zero-flow boundary conditions.
  
      Augment the set of control points with extra points on the
      boundary of the image that have zero flow.
  
      Args:
        control_point_locations: input control points.
        control_point_flows: their flows.
        image_height: image height.
        image_width: image width.
        boundary_points_per_edge: number of points to add in the middle of each
          edge (not including the corners).
          The total number of points added is
          `4 + 4*(boundary_points_per_edge)`.
  
      Returns:
        merged_control_point_locations: augmented set of control point locations.
        merged_control_point_flows: augmented set of control point flows.
      """
  
      batch_size = tf.shape(control_point_locations)[0]
  
      boundary_point_locations = _get_boundary_locations(
          image_height, image_width, boundary_points_per_edge
      )
  
      boundary_point_flows = tf.zeros(
          [tf.shape(boundary_point_locations)[0], 2]
      )
  
      type_to_use = control_point_locations.dtype
      boundary_point_locations = tf.cast(
          _expand_to_minibatch(boundary_point_locations, batch_size),
          type_to_use,
      )
  
      boundary_point_flows = tf.cast(
          _expand_to_minibatch(boundary_point_flows, batch_size),
          type_to_use,
      )
  
      merged_control_point_locations = tf.concat(
          [control_point_locations, boundary_point_locations], 1
      )
  
      merged_control_point_flows = tf.concat(
          [control_point_flows, boundary_point_flows], 1
      )
  
      return merged_control_point_locations, merged_control_point_flows
  
file_path: addons/tensorflow_addons/image/sparse_image_warp.py
imports: import tensorflow
  from tensorflow_addons.image import dense_image_warp
  from tensorflow_addons.image import interpolate_spline
  from tensorflow_addons.image import utils
  from tensorflow_addons.utils.types import TensorLike, FloatTensorLike
label_desc: Use image node_id 4 for calling a global function with example usage: _add_zero_flow_controls_at_boundary(control_point_locations, control_point_flows, image_height, image_width, boundary_points_per_edge) and returns: merged_control_point_locations,  merged_control_point_flows