code: def generate_migration(tables)
        return if tables.empty? && @db_tables.empty?
        result.clear
  
        add_line "Sequel.migration do"
        indent do
          generate_migration_body(tables)
        end
        add_line "end\n"
  
        result.join("\n")
      end
docs: Creates a migration builder for the given database.
  
   Generates a string of ruby code to define a sequel
   migration, based on the differences between the database schema
   of this MigrationBuilder and the tables passed.