def lb_lookup(session, lb_name):
    """Look up ELB Id by name

    Args:
        session (Session|None) : Boto3 session used to lookup information in AWS
                                 If session is None no lookup is performed
        lb_name (string) : Name of the ELB to lookup

    Returns:
        (bool) : If the lb_name is a valid ELB name
    """
    if session is None:
        return None

    lb_name = lb_name.replace('.', '-')

    ###
    # ELB
    client = session.client('elb')
    response = client.describe_load_balancers()
    for i in range(len(response['LoadBalancerDescriptions'])):
        if (response['LoadBalancerDescriptions'][i]['LoadBalancerName']) == lb_name:
            return True

    ###
    # ELB v2
    client = session.client('elbv2')
    response = client.describe_load_balancers()
    for i in range(len(response['LoadBalancers'])):
        if (response['LoadBalancers'][i]['LoadBalancerName']) == lb_name:
            return True

    return False