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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:

def get_service_policy(host, username, password, service_name, protocol=None, port=None, host_names=None):
    '''
    Get the service name's policy for a given host or list of hosts.

    host
        The location of the host.

    username
        The username used to login to the host, such as ``root``.

    password
        The password used to login to the host.

    service_name
        The name of the service for which to retrieve the policy. Supported service names are:
          - DCUI
          - TSM
          - SSH
          - lbtd
          - lsassd
          - lwiod
          - netlogond
          - ntpd
          - sfcbd-watchdog
          - snmpd
          - vprobed
          - vpxa
          - xorg

    protocol
        Optionally set to alternate protocol if the host is not using the default
        protocol. Default protocol is ``https``.

    port
        Optionally set to alternate port if the host is not using the default
        port. Default port is ``443``.

    host_names
        List of ESXi host names. When the host, username, and password credentials
        are provided for a vCenter Server, the host_names argument is required to tell
        vCenter the hosts for which to get service policy information.

        If host_names is not provided, the service policy information will be retrieved
        for the ``host`` location instead. This is useful for when service instance
        connection information is used for a single ESXi host.

    CLI Example:

    .. code-block:: bash

        # Used for single ESXi host connection information
        salt '*' vsphere.get_service_policy my.esxi.host root bad-password 'ssh'

        # Used for connecting to a vCenter Server
        salt '*' vsphere.get_service_policy my.vcenter.location root bad-password 'ntpd' \
        host_names='[esxi-1.host.com, esxi-2.host.com]'
    '''
    service_instance = salt.utils.vmware.get_service_instance(host=host,
                                                              username=username,
                                                              password=password,
                                                              protocol=protocol,
                                                              port=port)
    valid_services = ['DCUI', 'TSM', 'SSH', 'ssh', 'lbtd', 'lsassd', 'lwiod', 'netlogond',
                      'ntpd', 'sfcbd-watchdog', 'snmpd', 'vprobed', 'vpxa', 'xorg']
    host_names = _check_hosts(service_instance, host, host_names)

    ret = {}
    for host_name in host_names:
        # Check if the service_name provided is a valid one.
        # If we don't have a valid service, return. The service will be invalid for all hosts.
        if service_name not in valid_services:
            ret.update({host_name: {'Error': '{0} is not a valid service name.'.format(service_name)}})
            return ret

        host_ref = _get_host_ref(service_instance, host, host_name=host_name)
        services = host_ref.configManager.serviceSystem.serviceInfo.service

        # Don't require users to know that VMware lists the ssh service as TSM-SSH
        if service_name == 'SSH' or service_name == 'ssh':
            temp_service_name = 'TSM-SSH'
        else:
            temp_service_name = service_name

        # Loop through services until we find a matching name
        for service in services:
            if service.key == temp_service_name:
                ret.update({host_name:
                           {service_name: service.policy}})
                # We've found a match - break out of the loop so we don't overwrite the
                # Updated host_name value with an error message.
                break
            else:
                msg = 'Could not find service \'{0}\' for host \'{1}\'.'.format(service_name,
                                                                                host_name)
                ret.update({host_name: {'Error': msg}})

        # If we made it this far, something else has gone wrong.
        if ret.get(host_name) is None:
            msg = '\'vsphere.get_service_policy\' failed for host {0}.'.format(host_name)
            log.debug(msg)
            ret.update({host_name: {'Error': msg}})

    return ret