code: def add_tcp_firewall_rule(project, access_token, name, tag, port):
      
      
      headers = {
          'Authorization': 'Bearer %s' % access_token.access_token
      }
      
      payload = {
          "name": name,
          "kind": "compute#firewall",
          "sourceRanges": [ "0.0.0.0/0" ],
          "targetTags": [ tag ],
          "allowed": [ { "IPProtocol": "tcp", "ports": [ str(port), ] } ],
          "network": "projects/%s/global/networks/default" % project
      }
      
      r = requests.post('https://www.googleapis.com/compute/v1/'
                        'projects/%s/global/firewalls'
                        % project, headers=headers, json=payload)
      r.raise_for_status()
      op = r.json()['name']
  
      LOGGER.info('Requested to add firewall rule for tag "%s" '
                  '(operation "%s")...', tag, op)
  
      return op
docs: Adds a TCP firewall rule.
  
      TODO: docstring