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
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
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.