How to use the testinfra.get_host function in testinfra

import fnmatch
import json
import os

from six.moves import configparser

import testinfra
from testinfra.utils import cached_property
from testinfra.utils import check_ip_address
from testinfra.utils import TemporaryDirectory


__all__ = ['AnsibleRunner']

local = testinfra.get_host('local://')


def get_ansible_config():
    fname = os.environ.get('ANSIBLE_CONFIG')
    if not fname:
        for possible in (
            'ansible.cfg',
            os.path.join(os.path.expanduser('~'), '.ansible.cfg'),
            os.path.join('/', 'etc', 'ansible', 'ansible.cfg'),
        ):
            if os.path.exists(possible):
                fname = possible
                break
    config = configparser.ConfigParser()
    if not fname:
        return config

def get_ansible_host(config, inventory, host, ssh_config=None,
                     ssh_identity_file=None):
    if is_empty_inventory(inventory):
        if host == 'localhost':
            return testinfra.get_host('local://')
        return None
    hostvars = inventory['_meta'].get('hostvars', {}).get(host, {})
    connection = hostvars.get('ansible_connection', 'ssh')
    if connection not in (
        'smart', 'ssh', 'paramiko_ssh', 'local', 'docker', 'lxc', 'lxd',
    ):
        # unhandled connection type, must use force_ansible=True
        return None
    connection = {
        'lxd': 'lxc',
        'paramiko_ssh': 'paramiko',
        'smart': 'ssh',
    }.get(connection, connection)
    testinfra_host = hostvars.get('ansible_host', host)
    user = hostvars.get('ansible_user')
    password = hostvars.get('ansible_ssh_pass')

spec = '{}://'.format(connection)

    # Fallback to user:pasword auth when identity file is not used
    if user and password and not kwargs.get('ssh_identity_file'):
        spec += '{}:{}@'.format(user, password)
    elif user:
        spec += '{}@'.format(user)

    if check_ip_address(testinfra_host) == 6:
        spec += '[' + testinfra_host + ']'
    else:
        spec += testinfra_host
    if port:
        spec += ':{}'.format(port)
    return testinfra.get_host(spec, **kwargs)

def test_ssh_hostspec(hostspec, expected):
    backend = testinfra.get_host(hostspec).backend
    cmd, cmd_args = backend._build_ssh_command('true')
    command = backend.quote(' '.join(cmd), *cmd_args)
    assert command == expected

async def on_request_replied(self, req_data, gen_req, resp_or_exp):
        # start promoted node
        host = testinfra.get_host('ssh://persistent_node' + req_data['node_alias'][4:])
        host.run('sudo systemctl start indy-node')

async def on_request_replied(self, req_data, gen_req, resp_or_exp):
        # stop demoted node
        host = testinfra.get_host('ssh://persistent_node' + req_data['node_alias'][4:])
        host.run('sudo systemctl stop indy-node')