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: problem.rb
    path of file: ./repos/errbit/app/models
    
    the code of the file until where you have to start completion: # Represents a single Problem. The problem may have been
# reported as various Errs, but the user has grouped the
# Errs together as belonging to the same problem.

# rubocop:disable Metrics/ClassLength. At some point we need to break up this class, but I think it doesn't have to be right now.
class Problem
  include Mongoid::Document
  include Mongoid::Timestamps

  CACHED_NOTICE_ATTRIBUTES = {
    messages:    :message,
    hosts:       :host,
    user_agents: :user_agent_string
  }.freeze

  field :last_not
    
  def zero_filled_grouped_noticed_counts(since, group_by = 'day')
    non_zero_filled = grouped_notice_counts(since, group_by)
    buckets = group_by == 'day' ? 14 : 24

    ruby_time_method = group_by == 'day' ? :yday : :hour
    bucket_times = Array.new(buckets) { |ii| (since + ii.send(group_by)).send(ruby_time_method) }
    bucket_times.to_a.map do |bucket_time|
      count = if (data_for_day = non_zero_filled.detect { |item| item.dig('_id', group_by) == bucket_time })
                data_for_day['count']
              else
                0
              end
      { bucket_time => count }
    end