```ruby
class IncreaseTagSetNameColumnWidth < ActiveRecord::Migration
    change_table :iseq_flowcell do |t|
      t.change "tag_set_name",     :string,  limit: 100, comment:'WTSI-wide tag set name'
  end

  def down
    change_table :iseq_flowcell do |t|
      t.change  "tag_set_name",     :string,  limit: 50, comment:'WTSI-wide tag set name'
    end
  end
end
```

Fix missing method around migration
user
```ruby
class IncreaseTagSetNameColumnWidth < ActiveRecord::Migration

  def up
    change_table :iseq_flowcell do |t|
      t.change "tag_set_name",     :string,  limit: 100, comment:'WTSI-wide tag set name'
    end
  end

  def down
    change_table :iseq_flowcell do |t|
      t.change  "tag_set_name",     :string,  limit: 50, comment:'WTSI-wide tag set name'
    end
  end
end
```
assistant