code: def define_tables(cls, metadata):
      global people, engineers, managers, boss
      global companies, paperwork, machines
  
      companies = Table(
          "companies",
          metadata,
          Column(
              "company_id",
              Integer,
              primary_key=True,
              test_needs_autoincrement=True,
          ),
          Column("name", String(50)),
      )
  
      people = Table(
          "people",
          metadata,
          Column(
              "person_id",
              Integer,
              primary_key=True,
              test_needs_autoincrement=True,
          ),
          Column(
              "company_id", Integer, ForeignKey("companies.company_id")
          ),
          Column("name", String(50)),
          Column("type", String(30)),
      )
  
      engineers = Table(
          "engineers",
          metadata,
          Column(
              "person_id",
              Integer,
              ForeignKey("people.person_id"),
              primary_key=True,
          ),
          Column("status", String(30)),
          Column("engineer_name", String(50)),
          Column("primary_language", String(50)),
      )
  
      machines = Table(
          "machines",
          metadata,
          Column(
              "machine_id",
              Integer,
              primary_key=True,
              test_needs_autoincrement=True,
          ),
          Column("name", String(50)),
          Column(
              "engineer_id", Integer, ForeignKey("engineers.person_id")
          ),
      )
  
      managers = Table(
          "managers",
          metadata,
          Column(
              "person_id",
              Integer,
              ForeignKey("people.person_id"),
              primary_key=True,
          ),
          Column("status", String(30)),
          Column("manager_name", String(50)),
      )
  
      boss = Table(
          "boss",
          metadata,
          Column(
              "boss_id",
              Integer,
              ForeignKey("managers.person_id"),
              primary_key=True,
          ),
          Column("golf_swing", String(30)),
      )
  
      paperwork = Table(
          "paperwork",
          metadata,
          Column(
              "paperwork_id",
              Integer,
              primary_key=True,
              test_needs_autoincrement=True,
          ),
          Column("description", String(50)),
          Column("person_id", Integer, ForeignKey("people.person_id")),
      )
  
imports: from sqlalchemy import ForeignKey
  from sqlalchemy import Integer
  from sqlalchemy import String
  from sqlalchemy import util
  from sqlalchemy.orm import polymorphic_union
  from sqlalchemy.orm import relationship
  from sqlalchemy.orm import sessionmaker
  from sqlalchemy.sql.selectable import LABEL_STYLE_TABLENAME_PLUS_COL
  from sqlalchemy.testing import AssertsCompiledSQL
  from sqlalchemy.testing import config
  from sqlalchemy.testing import fixtures
  from sqlalchemy.testing.entities import ComparableEntity
  from sqlalchemy.testing.schema import Column
  from sqlalchemy.testing.schema import Table
label_desc: Use image node_id 1 for calling the _PolymorphicFixtureBase obj's underlying member method code with example usage: obj.define_tables(cls, metadata) without return types