```ruby
class Source < ApplicationRecord
  class UnknownRankable < StandardError; end
  has_many :imports
  validates :name, presence: true

  validates :email_rank, presence: true, uniqueness: true
  validates :location_rank, presence: true, uniqueness: true
  validates :organization_name_rank, presence: true, uniqueness: true
  validates :phone_number_rank, presence: true, uniqueness: true
  validates :website_rank, presence: true, uniqueness: true

  def rank_for(rankable)
    case rankable
    when Email then email_rank
    when Location then location_rank
    when OrganizationName then organization_name_rank
    when PhoneNumber then phone_number_rank
    when Website then website_rank
    else raise UnknownRankable
    end
  end
end
```

Add uniqueness validation to Source
user
```ruby
class Source < ApplicationRecord
  class UnknownRankable < StandardError; end
  has_many :imports

  validates :name, presence: true, uniqueness: true
  validates :email_rank, presence: true, uniqueness: true
  validates :location_rank, presence: true, uniqueness: true
  validates :organization_name_rank, presence: true, uniqueness: true
  validates :phone_number_rank, presence: true, uniqueness: true
  validates :website_rank, presence: true, uniqueness: true

  def rank_for(rankable)
    case rankable
    when Email then email_rank
    when Location then location_rank
    when OrganizationName then organization_name_rank
    when PhoneNumber then phone_number_rank
    when Website then website_rank
    else raise UnknownRankable
    end
  end
end
```
assistant