How to use the dxpy.find_one_data_object function in dxpy

rep2_control = ctl2_ta  # default.  May be changed later.
    rep2_ctl_msg = "control rep2"

    rep_info = [(ntags_rep1, 'replicate 1', rep1_ta_filename)]
    if not simplicate_experiment:
        rep_info.append((ntags_rep2, 'replicate 2', rep2_ta_filename))
    rep_info.extend(
        [(ntags_ctl1, 'control 1', ctl1_ta_filename),
         (ntags_ctl2, 'control 2', ctl2_ta_filename)])
    for n, name, filename in rep_info:
        logger.info("Found %d tags in %s file %s" % (n, name, filename))

    subprocess.check_output('ls -l', shell=True, stderr=subprocess.STDOUT)

    if not simplicate_experiment:
        pool_applet = dxpy.find_one_data_object(
                classname='applet',
                name='pool',
                project=dxpy.PROJECT_CONTEXT_ID,
                zero_ok=False,
                more_ok=False,
                return_handler=True)
        pool_replicates_subjob = \
            pool_applet.run(
                {"inputs": [rep1_ta, rep2_ta],
                 "prefix": 'pooled_reps'},
                name='Pool replicates')
        pooled_replicates = pool_replicates_subjob.get_output_ref("pooled")
        pooled_replicates_xcor_subjob = \
            xcor_only(
                pooled_replicates,
                paired_end,

def find_reference_file_by_name(reference_name, project_name):
    '''Looks up a reference file by name in the project that holds common tools. From Joe Dale's code.'''
    project = dxpy.find_one_project(name=project_name, name_mode='exact', return_handler=False)
    cached = '*'
    if (reference_name, project['id']) not in REFERENCE_FILES:
        found = dxpy.find_one_data_object(classname="file", name=reference_name,
                                          project=project['id'],
                                          recurse=True,
                                          zero_ok=False, more_ok=False, return_handler=True)
        REFERENCE_FILES[(reference_name, project['id'])] = found
        cached = ''

    print cached + "Resolved %s to %s" % (reference_name, REFERENCE_FILES[(reference_name, project['id'])].get_id())
    return dxpy.dxlink(REFERENCE_FILES[(reference_name, project['id'])])

def find_applet_by_name(applet_name, applets_project_id):
    '''Looks up an applet by name in the project that holds tools.
      From Joe Dale's code.'''
    cached = '*'
    if (applet_name, applets_project_id) not in APPLETS:
        found = dxpy.find_one_data_object(
            classname="applet",
            name=applet_name,
            project=applets_project_id,
            zero_ok=False,
            more_ok=False,
            return_handler=True)
        APPLETS[(applet_name, applets_project_id)] = found
        cached = ''

    logging.info(
        cached + "Resolved applet %s to %s"
        % (applet_name, APPLETS[(applet_name, applets_project_id)].get_id()))
    return APPLETS[(applet_name, applets_project_id)]

try:
            project_handler = resolve_project(DATA_CACHE_PROJECT)
            snapshot_project = project_handler
        except:
            logger.error("Cannot find cache project %s" % (DATA_CACHE_PROJECT))
            snapshot_project = None

        logger.debug('Cache project: %s' % (snapshot_project))

        if snapshot_project:
            try:
                accession_search = accession + '*'
                logger.debug(
                    'Looking recursively for %s in %s'
                    % (accession_search, snapshot_project.name))
                file_handler = dxpy.find_one_data_object(
                    name=accession_search, name_mode='glob', more_ok=False,
                    classname='file', recurse=True, return_handler=True,
                    folder='/', project=snapshot_project.get_id())
                logger.debug('Got file handler for %s' % (file_handler.name))
                return file_handler
            except:
                logger.debug(
                    "Cannot find accession %s in project %s"
                    % (accession, snapshot_project))

    # we're here because we couldn't find the cache or couldn't find the file
    # in the cache, so look in AWS

    # this returns a link to the file in the applet's project context
    dx_file = s3_dxcp(accession, server, keypair)

logger.debug("Now looking for file %s" % (file_identifier))

    m = re.match(r'''(^[\w\-\ /\.]+)/([\w\-\ \.]+)''', file_identifier)
    if m:
        folder_name = m.group(1)
        if not folder_name.startswith('/'):
            folder_name = '/' + folder_name
        file_name = m.group(2)
    else:
        folder_name = '/fastqs/'
        file_name = file_identifier + '.fastq.gz'

    logger.debug("Looking for file %s in folder %s" % (file_name, folder_name))

    try:
        file_handler = dxpy.find_one_data_object(
            name=file_name, folder=folder_name, project=project.get_id(),
            more_ok=False, zero_ok=False, return_handler=True)
    except:
        logger.debug(
            '%s not found in project %s folder %s'
            % (file_name, project.get_id(), folder_name))
        try:  # maybe it's just  filename in the default workspace
            file_handler = dxpy.DXFile(dxid=identifier, mode='r')
        except:
            logger.debug('%s not found as a dxid' % (identifier))
            file_handler = resolve_accession(identifier, server, keypair)

    assert file_handler, "Failed to resolve file identifier %s" % (identifier)
    logger.debug(
        "Resolved file identifier %s to %s" % (identifier, file_handler.name))

def resolve_dx_file(identifier):
    try:
        handler = dxpy.get_handler(identifier)
    except dxpy.DXError:
        try:
            handler = dxpy.find_one_data_object(
                classname='file',
                name=identifier,
                return_handler=True,
                zero_ok=False,
                more_ok=False)
        except dxpy.DXSearchError:
            logging.error('Failed to resolve control %s to unique dx object.  ID or name does not exist or multiple files of that name were found.' % (str(identifier)))
            return None
        else:
            return handler
    else:
        return handler

if m:
        folder_name = m.group(1)
        if not folder_name.startswith('/'):
            folder_name = '/' + folder_name
        recurse = False
        file_name = m.group(2)
    else:
        folder_name = '/'
        recurse = True
        file_name = file_identifier

    logging.debug(
        "Looking for file %s in folder %s" % (file_name, folder_name))

    try:
        file_handler = dxpy.find_one_data_object(
            name=file_name,
            folder=folder_name,
            project=project.get_id(),
            recurse=recurse,
            more_ok=False,
            zero_ok=False,
            return_handler=True)
    except dxpy.DXSearchError:
        logging.debug(
            '%s not found in project %s folder %s.  Trying as file ID'
            % (file_name, project.get_id(), folder_name))
        file_handler = None
    except:
        raise

    if not file_handler: