@startuml


top to bottom direction
skinparam linetype ortho

package base {

  abstract Base {
    + id\t\t\t\tInteger\t\t<<PK>>  {field}
    # __tablename__\tstr   {field}
  }

  object to_snake_case {
    name\tstr
  }

  object bidirectional_relationship {
    cls\t\t\t\tclass
    foreign_table_cls\tclass
  }

 }
@enduml