i am creating a dataset for real time face recognition using python. i want it should intimate if the image already available in dataset. how to implement in opencv?

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import cv2
from PIL import Image
import os
import time

face_cascade = cv2.CascadeClassifier("haarcascade_frontalface_default.xml")
ds_factor = 0.6
font = cv2.FONT_HERSHEY_SIMPLEX

dir_path = "static/capture_image"


class VideoCamera(object):
    def __init__(self):
        self.video = cv2.VideoCapture(0)

    def __del__(self):
        self.video.release()

    def get_frame(self):
        success, image = self.video.read()
        output = image.copy()
        cv2.rectangle(image, (400, 300), (800, 600), (255, 255, 255), 2)
        cv2.addWeighted(image, 0.5, output, 1 - .5, 0, output)
        cv2.resize(output, None, fx=ds_factor, fy=ds_factor, interpolation=cv2.INTER_AREA)
        gray = cv2.cvtColor(output, cv2.COLOR_BGR2GRAY)
        roi = gray[300:600, 400:800]  # ymin,ymax, xmin,xmax !

        faces = face_cascade.detectMultiScale(
            roi, scaleFactor=1.1,
            minNeighbors=5,
            minSize=(200, 200),
            flags=cv2.CASCADE_SCALE_IMAGE)

        for (x, y, w, h) in faces:
            cv2.rectangle(output, (x + 400, y + 300), (x + 400 + w, y + 300 + h), (255, 0, 0), 3)
            cv2.putText(output, 'Number of Faces : ' + str(len(faces)), (40, 40), font, 1, (255, 0, 0), 2)
            face_image = gray[y+300:y + 300 + h, x + 400:x + 400 + w]
            pil_image = Image.fromarray(face_image)
            File_Formatted = ("%s" % (y+300)) + ".jpg"
            file_path = os.path.join(dir_path, File_Formatted)
            pil_image.save(file_path)
            break
        ret, jpeg = cv2.imencode('.jpg', output)
        return jpeg.tobytes()