new_contents: """add update time
  
  Revision ID: f4c55277bc6f
  Revises: f5d707713ae0
  Create Date: 2017-04-02 14:22:31.534188
  
  """
  from alembic import op
  import sqlalchemy as sa
  
  
  # revision identifiers, used by Alembic.
  revision = 'f4c55277bc6f'
  down_revision = 'f5d707713ae0'
  branch_labels = None
  depends_on = None
  
  
  def upgrade():
      # ### commands auto generated by Alembic - please adjust! ###
      op.add_column('mqtt_items', sa.Column('update_time', sa.DateTime(), nullable=True))
      # ### end Alembic commands ###
  
  
  def downgrade():
      # ### commands auto generated by Alembic - please adjust! ###
      op.drop_column('mqtt_items', 'update_time')
      # ### end Alembic commands ###
  
subject: Add database changes