Provided are an agitator and an agitating hook provided therein. The diffraction grating is a chirped grating having a refractive index with a period continuously changing along the optical axis direction of optical fiber, whereas the amplitude of refractive index of the chirped grating changes so as to draw an envelope along the light-guiding direction. A rechargeable lithium-ion battery provides power for the flashlight. The resulting structure is rigid and does not twist. In an example embodiment, the paying party compares the patient provided information with the invoice received from the healthcare provider to assess the accuracy of the invoice.