def upgrade():
    ### commands auto generated by Alembic - please adjust! ###
    op.add_column('events', sa.Column('ical_url', sa.String(), nullable=True))
    op.add_column('events', sa.Column('pentabarf_url', sa.String(), nullable=True))
    op.add_column('events', sa.Column('xcal_url', sa.String(), nullable=True))