code: def downgrade():
      conn = op.get_bind()
      inspector = inspect(conn)
      tables = inspector.get_table_names()
      if "sensor_instance" in tables:
          op.drop_table("sensor_instance")
  
imports: from __future__ import annotations
  import sqlalchemy
  from alembic import op
  from sqlalchemy import func, inspect
  from airflow.migrations.db_types import TIMESTAMP, StringID
label_desc: Use image node_id 2 for calling a global function with example usage: downgrade() without return types