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    <File>osmt-20191231.xsd</File>
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    <File>osmt-20191231_def.xml</File>
    <File>osmt-20191231_lab.xml</File>
    <File>osmt-20191231_pre.xml</File>
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  <BaseTaxonomies>
    <BaseTaxonomy>http://fasb.org/srt/2019-01-31</BaseTaxonomy>
    <BaseTaxonomy>http://xbrl.sec.gov/dei/2019-01-31</BaseTaxonomy>
    <BaseTaxonomy>http://fasb.org/us-gaap/2019-01-31</BaseTaxonomy>
  </BaseTaxonomies>
  <HasPresentationLinkbase>true</HasPresentationLinkbase>
  <HasCalculationLinkbase>true</HasCalculationLinkbase>
</FilingSummary>
