code: def upgrade():
      conn = op.get_bind()
      if conn.dialect.name == "mysql":
          op.alter_column(
              table_name="dag_code",
              column_name="source_code",
              type_=mysql.MEDIUMTEXT,
              nullable=False,
          )
  
imports: from __future__ import annotations
  from alembic import op
  from sqlalchemy.dialects import mysql
label_desc: Use image node_id 1 for calling a global function with example usage: upgrade() without return types