How can I update charts in real-time while using MongoDB changes to pull new data?

This code works but the same document gets returned multiple times. What supposed to happen is an array of [1,2,3,...] in the x-axis and [1,2,3,4, .....] in the y-axis gets plotted. However, Y is sometimes returned as [1,0,0,1,1,2,3,3,4,5,5,5,].What can I do to fix this? This code works but the same document gets returned multiple times. What supposed to happen is an array of [1,2,3,...] in the x-axis and [1,2,3,4, .....] in the y-axis gets plotted. However, Y is sometimes returned as [1,0,0,1,1,2,3,3,4,5,5,5,].What can I do to fix this?

import dash
from dash.dependencies import Output, Event
import dash_core_components as dcc
import dash_html_components as html
import plotly
import random
from plotly import graph_objs
from collections import deque    # Define max size
import pymongo
import constants
import logging
from collections import OrderedDict


client = pymongo.MongoClient(constants.MONGODB_CONN)
X = []
Y = []
X.append(1)
Y.append(1)
count = 0
resume_token = 'NEW'
token_holder = []
stream = client.changestream.collection.watch()

app = dash.Dash(__name__)
app.layout = html.Div([
    dcc.Graph(id='live-graph', animate=True),
    dcc.Interval(
        id='graph-update',
        interval=1000
    )
])


@app.callback(Output('live-graph', 'figure'),
              events=[Event('graph-update', 'interval')])
def update_graph():
    global stream
    global token_holder
    global X
    global Y
    global client
    global resume_token
    if resume_token is "NEW":
        print('NEW DONE NEW DONE NEW DONE NEW DONE')

        for insert_change in stream:
            resume_token = stream.resume_token
            # print('Working 3')
            # print(change['fullDocument']['hello'])
            # print('Working 4')
            print('')  # for readability only
            X.append(X[-1] + 1)
            Y.append(insert_change['fullDocument']['hello'])
            print(insert_change['fullDocument']['hello'])
            print(X)
            # print(Y)
            # token_holder.append(resume_token)
            data = graph_objs.Scatter(
                x=list(X),
                y=list(Y),
                name='Scatter',
                mode='markers'
            )
            return {'data': [data], 'layout': graph_objs.Layout(xaxis=dict(range=[min(X), max(X)]),
                                                                    yaxis=dict(range=[min(Y), max(Y)]))}
    else:
        for insert_change in stream:
            # token_holder.append(resume_token)
            # print('Working 3')
            # print(change['fullDocument']['hello'])
            # print('Working 4')
            # print('')  # for readability only
            X.append(X[-1] + 1)
            Y.append(insert_change['fullDocument']['hello'])
            print(insert_change['fullDocument']['hello'])
            print(X)
            print(Y)
            if resume_token in token_holder:
                resume_token = stream.resume_token
                token_holder.append(resume_token)
                data = graph_objs.Scatter(
                    x=list(X),
                    y=list(Y),
                    name='Scatter',
                    mode='markers'
                )
                return {'data': [data], 'layout': graph_objs.Layout(xaxis=dict(range=[min(X), max(X)]),
                                                                yaxis=dict(range=[min(Y), max(Y)]))}

if __name__ == "__main__":
    app.run_server(debug=True)