code: def _axis_angle_to_quaternion(axis, angle):
      """Converts an axis-angle representation to a quaternion.
  
      Args:
        axis: The axis of rotation.
        angle: The angle.
  
      Returns:
        The quaternion.
      """
      quat = np.zeros(4)
      quat[0:3] = axis * np.sin(0.5 * angle)
      quat[3] = np.cos(0.5 * angle)
      return quat
  
imports: import numpy
label_desc: Use image node_id 2 for calling a global function with example usage: _axis_angle_to_quaternion(axis, angle) and returns: quat