def format_report(count, new_inst, del_inst, svc_info):
    """
    Given a service's new, deleted inst, return a string representation for email
    """
    needed = False
    body = ''
    if new_inst is not None and len(new_inst) > 0:
        needed = True
        body += '\n\n  New Instances: '
        for inst in new_inst:
            body += '\n    ' + inst['myname']
    else:
        body += '\n\n  No new instances.'
    if del_inst is not None and len(del_inst) > 0:
        needed = True
        body += '\n\n  Deleted Instances: '
        for inst in del_inst:
            body += '\n    ' + inst['myname']
    else:
        body += '\n\n  No deleted instances.'
    if needed:
        output = 'Service: ' + svc_info['Service']
        output += '\n  Total Instances: ' + str(count)
        output += '\n\n'
        return output + body

    return None