数据基本上都是科研论文，格式是 xml，我想把这些文章转化为 BSON，然后存在 mongoDB 中。

层级太多没关系吧，嵌套了大概 5 层，写 model 估计会累死。

<PubmedArticle>
    <MedlineCitation Owner="NLM" Status="PubMed-not-MEDLINE">
        <PMID Version="1">23094252</PMID>
        <DateCreated>
            <Year>2012</Year>
            <Month>10</Month>
            <Day>24</Day>
        </DateCreated>
        <DateCompleted>
            <Year>2012</Year>
            <Month>10</Month>
            <Day>25</Day>
        </DateCompleted>
        <Article PubModel="Print-Electronic">
            <Journal>
                <ISSN IssnType="Electronic">2234-6171</ISSN>
                <JournalIssue CitedMedium="Internet">
                    <Volume>39</Volume>
                    <Issue>5</Issue>
                    <PubDate>
                        <Year>2012</Year>
                        <Month>Sep</Month>
                    </PubDate>
                </JournalIssue>
                <Title>Archives of plastic surgery</Title>
                <ISOAbbreviation>Arch Plast Surg</ISOAbbreviation>
            </Journal>
            <ArticleTitle>Usefulness of Intravenous Anesthesia Using a Target-controlled Infusion System with Local Anesthesia in Submuscular Breast Augmentation Surgery.</ArticleTitle>
            <Pagination>
                <MedlinePgn>540-5</MedlinePgn>
            </Pagination>
            <ELocationID EIdType="doi" ValidYN="Y">10.5999/aps.2012.39.5.540</ELocationID>
            <Abstract>
                <AbstractText Label="BACKGROUND" NlmCategory="BACKGROUND">Patients have anxiety and fear of complications due to general anesthesia. Through new instruments and local anesthetic drugs, a variety of anesthetic methods have been introduced. These methods keep hospital costs down and save time for patients. In particular, the target-controlled infusion (TCI) system maintains a relatively accurate level of plasma concentration, so the depth of anesthesia can be adjusted more easily. We conducted this study to examine whether intravenous anesthesia using the TCI system with propofol and remifentanil would be an effective method of anesthesia in breast augmentation.</AbstractText>
                <AbstractText Label="METHODS" NlmCategory="METHODS">This study recruited 100 patients who underwent breast augmentation surgery from February to August 2011. Intravenous anesthesia was performed with 10 mg/mL propofol and 50 µg/mL remifentanil simultaneously administered using two separate modules of a continuous computer-assisted TCI system. The average target concentration was set at 2 µg/mL and 2 ng/mL for propofol and remifentanil, respectively, and titrated against clinical effect and vital signs. Oxygen saturation, electrocardiography, and respiratory status were continuously measured during surgery. Blood pressure was measured at 5-minute intervals. Information collected includes total duration of surgery, dose of drugs administered during surgery, memory about surgery, and side effects.</AbstractText>
                <AbstractText Label="RESULTS" NlmCategory="RESULTS">Intraoperatively, there was transient hypotension in two cases and hypoxia in three cases. However, there were no serious complications due to anesthesia such as respiratory difficulty, deep vein thrombosis, or malignant hypertension, for which an endotracheal intubation or reversal agent would have been needed. All the patients were discharged on the day of surgery and able to ambulate normally.</AbstractText>
                <AbstractText Label="CONCLUSIONS" NlmCategory="CONCLUSIONS">Our results indicate that anesthetic methods, where the TCI of propofol and remifentanil is used, might replace general anesthesia with endotracheal intubation in breast augmentation surgery.</AbstractText>
            </Abstract>
            <Affiliation>Department of Plastic and Reconstructive Surgery, Yeungnam University Hospital, Yeungnam University College of Medicine, Daegu, Korea.</Affiliation>
            <AuthorList CompleteYN="Y">
                <Author ValidYN="Y">
                    <LastName>Chung</LastName>
                    <ForeName>Kyu-Jin</ForeName>
                    <Initials>KJ</Initials>
                </Author>
                <Author ValidYN="Y">
                    <LastName>Cha</LastName>
                    <ForeName>Kyu-Ho</ForeName>
                    <Initials>KH</Initials>
                </Author>
                <Author ValidYN="Y">
                    <LastName>Lee</LastName>
                    <ForeName>Jun-Ho</ForeName>
                    <Initials>JH</Initials>
                </Author>
                <Author ValidYN="Y">
                    <LastName>Kim</LastName>
                    <ForeName>Yong-Ha</ForeName>
                    <Initials>YH</Initials>
                </Author>
                <Author ValidYN="Y">
                    <LastName>Kim</LastName>
                    <ForeName>Tae-Gon</ForeName>
                    <Initials>TG</Initials>
                </Author>
                <Author ValidYN="Y">
                    <LastName>Kim</LastName>
                    <ForeName>Il-Guk</ForeName>
                    <Initials>IG</Initials>
                </Author>
            </AuthorList>
            <Language>eng</Language>
            <PublicationTypeList>
                <PublicationType>Journal Article</PublicationType>
            </PublicationTypeList>
            <ArticleDate DateType="Electronic">
                <Year>2012</Year>
                <Month>09</Month>
                <Day>12</Day>
            </ArticleDate>
        </Article>
        <MedlineJournalInfo>
            <Country>Korea (South)</Country>
            <MedlineTA>Arch Plast Surg</MedlineTA>
            <NlmUniqueID>101577999</NlmUniqueID>
            <ISSNLinking>2234-6163</ISSNLinking>
        </MedlineJournalInfo>
    </MedlineCitation>
    <PubmedData>
        <History>
            <PubMedPubDate PubStatus="received">
                <Year>2012</Year>
                <Month>5</Month>
                <Day>31</Day>
            </PubMedPubDate>
            <PubMedPubDate PubStatus="revised">
                <Year>2012</Year>
                <Month>8</Month>
                <Day>14</Day>
            </PubMedPubDate>
            <PubMedPubDate PubStatus="accepted">
                <Year>2012</Year>
                <Month>8</Month>
                <Day>14</Day>
            </PubMedPubDate>
            <PubMedPubDate PubStatus="epublish">
                <Year>2012</Year>
                <Month>9</Month>
                <Day>12</Day>
            </PubMedPubDate>
            <PubMedPubDate PubStatus="entrez">
                <Year>2012</Year>
                <Month>10</Month>
                <Day>25</Day>
                <Hour>6</Hour>
                <Minute>0</Minute>
            </PubMedPubDate>
            <PubMedPubDate PubStatus="pubmed">
                <Year>2012</Year>
                <Month>10</Month>
                <Day>25</Day>
                <Hour>6</Hour>
                <Minute>0</Minute>
            </PubMedPubDate>
            <PubMedPubDate PubStatus="medline">
                <Year>2012</Year>
                <Month>10</Month>
                <Day>25</Day>
                <Hour>6</Hour>
                <Minute>0</Minute>
            </PubMedPubDate>
        </History>
        <PublicationStatus>ppublish</PublicationStatus>
        <ArticleIdList>
            <ArticleId IdType="doi">10.5999/aps.2012.39.5.540</ArticleId>
            <ArticleId IdType="pubmed">23094252</ArticleId>
        </ArticleIdList>
    </PubmedData>
</PubmedArticle>