old_contents: """
  Copyright [2009-2017] EMBL-European Bioinformatics Institute
  Licensed under the Apache License, Version 2.0 (the "License");
  you may not use this file except in compliance with the License.
  You may obtain a copy of the License at
       http://www.apache.org/licenses/LICENSE-2.0
  Unless required by applicable law or agreed to in writing, software
  distributed under the License is distributed on an "AS IS" BASIS,
  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  See the License for the specific language governing permissions and
  limitations under the License.
  """
  
  from django.db import models
  
  
  class SecondaryStructure(models.Model):
      id = models.AutoField(primary_key=True)
      accession = models.ForeignKey(
          'Accession',
          db_column='rnc_accession_id',
          to_field='accession',
          related_name='secondary_structure',
      )
      secondary_structure = models.TextField()
      md5 = models.CharField(max_length=32, db_index=True)
  
      class Meta:
          db_table = 'rnc_secondary_structure'
          unique_together = (('accession', 'md5'),)
  
new_contents: """
  Copyright [2009-2017] EMBL-European Bioinformatics Institute
  Licensed under the Apache License, Version 2.0 (the "License");
  you may not use this file except in compliance with the License.
  You may obtain a copy of the License at
       http://www.apache.org/licenses/LICENSE-2.0
  Unless required by applicable law or agreed to in writing, software
  distributed under the License is distributed on an "AS IS" BASIS,
  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  See the License for the specific language governing permissions and
  limitations under the License.
  """
  
  from django.db import models
  
  
  class SecondaryStructure(models.Model):
      id = models.AutoField(primary_key=True)
      accession = models.OneToOneField(
          'Accession',
          db_column='rnc_accession_id',
          to_field='accession',
          related_name='secondary_structure',
      )
      secondary_structure = models.TextField()
      md5 = models.CharField(max_length=32, db_index=True)
  
      class Meta:
          db_table = 'rnc_secondary_structure'
          unique_together = (('accession', 'md5'),)
  
subject: Use OneToOneField on SecondaryStructure model