docs: def get_file(self, repository_fname):
          """
          Retrieve an existing :class:`meteorpi_model.FileRecord` by its ID
  
          :param string repository_fname:
              The file ID
          :return:
              A :class:`meteorpi_model.FileRecord` instance, or None if not found
          """
          search = mp.FileRecordSearch(repository_fname=repository_fname)
          b = search_files_sql_builder(search)
          sql = b.get_select_sql(columns='f.uid, o.publicId AS observationId, f.mimeType, '
                                         'f.fileName, s2.name AS semanticType, f.fileTime, '
                                         'f.fileSize, f.fileMD5, l.publicId AS obstory_id, l.name AS obstory_name, '
                                         'f.repositoryFname',
                                 skip=0, limit=1, order='f.fileTime DESC')
          files = list(self.generators.file_generator(sql=sql, sql_args=b.sql_args))
          if not files:
              return None
          return files[0]