You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: post_vote.rb
    path of file: ./repos/e621ng/app/models
    
    the code of the file until where you have to start completion: # frozen_string_literal: true

class PostVote < UserVote
  validate :validate_user_can_vote

  def self.model_creator_column
    :uploader
  
    
  def validate_user_can_vote
    if user.younger_than(3.days) && score == -1
      errors.add(:user, "must be 3 days old to downvote posts")
      return false
    end
    allowed = user.can_post_vote_with_reason
    if allowed != true
      errors.add(:user, User.throttle_reason(allowed))
      return false
    end