こちらを参考にしました。
ドキュメントの追加

put_firestore_docs.py

#! /usr/bin/python
#
#	put_firestore_docs.py
#
#						Apr/02/2022
# ------------------------------------------------------------------
import sys
import json
import ndjson
import firebase_admin
from firebase_admin import credentials
from firebase_admin import firestore
from datetime import date, datetime
# ------------------------------------------------------------------
def file_to_str_proc(file_in):
	str_out = ""
	try:
		fp_in = open(file_in,encoding='utf-8')
		str_out = fp_in.read()
		fp_in.close()
	except Exception as ee:
		sys.stderr.write("*** error *** file_to_str_proc ***\n")
		sys.stderr.write(str (ee))
#
	return	str_out
# ------------------------------------------------------------------
sys.stderr.write("*** 開始 ***\n")

file_ndjson=sys.argv[1]
sys.stderr.write(file_ndjson + "\n")

str_in = file_to_str_proc(file_ndjson)

data = ndjson.loads(str_in)

project_id='project-apr02-2022'
collection_in='sample_collection'

cred = credentials.ApplicationDefault()
firebase_admin.initialize_app(cred, {
	'projectId': project_id
})

db = firestore.client()

count = 0
for unit in data:
	print(count)
#	print(unit['senderId'])
#	print()
	db.collection(collection_in).add(unit)
	count += 1

sys.stderr.write("*** 終了 ***\n")
# ------------------------------------------------------------------

実行スクリプト

export GOOGLE_APPLICATION_CREDENTIALS="key-file-apr02.json"
./put_firestore_docs.py in01.ndjson