headers = {
    'Accept': '*/*',
    'Content-Type': 'application/json',
    'X-Cisco-Meraki-API-Key': '**********************'
}

data = {
    'rules': [
        {
            'comment': 'Example',
            'policy': 'allow',
            'protocol': 'tcp',
            'srcPort': 'any',
            'srcCidr': 'any',
            'destPort': '53',
            'destCidr': '8.8.8.8/32',
            'syslogEnabled': 'True'
        }
    ]
}

url = 'https://api.meraki.com/api/v0/networks/<< NETWORK >>/l3FirewallRules'
r = requests.put(url=url, headers=headers, verify=False, json=data)