how to check if the output net buffer is empty?

[FeelUsM]

I am sending a lot of data for online rendering of the heatmap plot,
and at the same time the buffer fills up and the interface begins to lag behind the backend.
And in some cases even an error occurs

The Jupyter server will temporarily stop sending output
to the client in order to avoid crashing it.
To change this limit, set the config variable
`--ServerApp.iopub_msg_rate_limit`.

Current values:
ServerApp.iopub_msg_rate_limit=1000.0 (msgs/sec)
ServerApp.rate_limit_window=3.0 (secs)

Is there way to check if the buffer has unsent data to avoid sending data too often?

---

Now I've come up with a crutch: ping every 60 frames.

class PingWidget(anywidget.AnyWidget):
	_esm = Path("ping.js").read_text(encoding="utf-8")
	ping = tBool().tag(sync=True)
	pong = tBool().tag(sync=True)

ping = PingWidget()
ping

h, w = 50, 150
wgt = HeatmapWidget(height=h, width=w, cell_size=4) # my custom widget
wgt.draw(np.random.rand(h, w)*2-1)
wgt

import time
skipped = 0
t0 = time.time()
t1 = time.time()
N=500
i=0
while i<N:
	if i%60==0:
		while ping.ping!=ping.pong:
			time.sleep(0.07)
			skipped +=1
		ping.ping = not ping.ping
	if time.time()-t1>0.02:
		wgt.draw(np.random.rand(h, w)*2-1)
		t1 = time.time()
		i+=1
	time.sleep(0.005)
skipped, N/(time.time()-t0)

but this leads to friezes every second.
(and if you ping every frame, fps drops from 40 to 10)
In fact, I don't have to wait for a response from the frontend.
I want to send data one way at maximum speed so that the buffer doesn't get clogged.