code: def upgrade():
      """Apply Add ``dag_hash`` Column to ``serialized_dag`` table"""
      op.add_column(
          "serialized_dag",
          sa.Column(
              "dag_hash",
              sa.String(32),
              nullable=False,
              server_default="Hash not calculated yet",
          ),
      )
  
imports: from __future__ import annotations
  import sqlalchemy
  from alembic import op
label_desc: Use image node_id 1 for calling a global function with example usage: upgrade() without return types