Where is create_table method defined?

Hi

When scaffolding a model with Rails, you will get a migration file,
say 001_create_items.rb
that looks something like this:

class CreateItems < ActiveRecord::Migration
  def self.up
    create_table :items do |t|
      ...
    end
  end

  def self.down
    drop_table :items
  end
end

My question is: Where is this method 'create_table' defined in Rails?
I was expecting to find it in the superclass ActiveRecord::Migration
which I think is defined in file .../lib/active_record/migration.rb
But I cannot find it there.

Anyone has a clue?

TIA
------------- grz01