invite user by username to telegram channel

i trying to add users by usernames to my channel. I am using python 3.6 telethon library and pythonanywhere server:

api_hash = 'b7**'
phone = '+7***'
client = TelegramClient('new_ses', api_id, api_hash)
client.connect()
client = TelegramClient('session_neworig', api_id, api_hash,)
client.connect()

from telethon.tl.functions.channels import InviteToChannelRequest
from telethon.tl.functions.contacts import ResolveUsernameRequest
from telethon.tl.types import InputPeerChannel ,InputPeerUser,InputUser
from telethon.tl.functions.channels import JoinChannelRequest

chann=client.get_entity('channelname') #its public channel
print(chann.id)
1161823752

print(chann.access_hash)
8062085565372622341

time.sleep(30)
chan=InputPeerChannel(chann.id, chann.access_hash)
user = client(ResolveUsernameRequest('Chai***'))


print(user.users[0].id)
193568760
print(user.users[0].access_hash)
-4514649540347033311
time.sleep(1*30)

user=InputUser(user.users[0].id,user.users[0].access_hash,)

client.invoke(InviteToChannelRequest(chan,[user]))

This dosent work and i get -telethon.errors.rpc_error_list.PeerFloodError: (PeerFloodError(...), 'Too many requests')

what am i doing wrong? how to avoid it ? this one code is worked for me , but i am gone to flood after added let's say 20 users :

 from telethon.helpers import get_input_peer

client.invoke(InviteToChannelRequest(
    get_input_peer(client.get_entity(chan),
    [get_input_peer(client.get_entity(user))]
))

Please help , how to add 200 users by username without any ban , maybe there is another way to do it by python ? another lib or by api ?