code: def upgrade():
      bind = op.get_bind()
      op.add_column(
          "tables",
          sa.Column(
              "is_sqllab_view",
              sa.Boolean(),
              nullable=True,
              default=False,
              server_default=sa.false(),
          ),
      )
  
      session = db.Session(bind=bind)
  
      # Use Slice class defined here instead of models.Slice
      for tbl in session.query(Table).all():
          if tbl.sql:
              tbl.is_sqllab_view = True
  
      session.commit()
      db.session.close()
  
file_path: superset/superset/migrations/versions/2018-04-03_08-19_130915240929_is_sqllab_viz_flow.py
imports: import sqlalchemy
  from alembic import op
  from sqlalchemy.ext.declarative import declarative_base
  from superset import db
label_desc: Use image node_id 1 for calling a global function with example usage: upgrade() without return types