old_contents: """Add subtitle field to post database.
  
  Revision ID: d15f6cac07e1
  Revises: 009eafe4838f
  Create Date: 2018-10-03 12:31:18.462880
  
  """
  
  # revision identifiers, used by Alembic.
  revision = 'd15f6cac07e1'
  down_revision = '009eafe4838f'
  
  from alembic import op
  import sqlalchemy as sa
  
  
  def upgrade():
      op.add_column('posts', sa.Column('subtitle', sa.Text(), nullable=True))
  
  
  def downgrade():
      op.drop_column('posts', 'subtitle')
  
new_contents: """Add subtitle field to post database.
  
  Revision ID: d15f6cac07e1
  Revises: 009eafe4838f
  Create Date: 2018-10-03 12:31:18.462880
  
  """
  
  # revision identifiers, used by Alembic.
  import sqlalchemy as sa
  from alembic import op
  revision = 'd15f6cac07e1'
  down_revision = '009eafe4838f'
  
  
  def upgrade():
      op.add_column('posts', sa.Column('subtitle', sa.Text(), nullable=True))
  
  
  def downgrade():
      op.drop_column('posts', 'subtitle')
  
subject: update db migration