Show the details of the existing instance.

def show_instance(vm_name, call=None):
    '''
    Show the details of the existing instance.
    '''
    if call != 'action':
        raise SaltCloudSystemExit(
            'The show_instance action must be called with -a or --action.'
        )
    conn = get_conn()
    node = _expand_node(conn.ex_get_node(vm_name))
    __utils__['cloud.cache_node'](node, __active_provider_name__, __opts__)
    return node