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: progression.rb
    path of file: ./repos/coltrane/lib/coltrane/theory
    
    the code of the file until where you have to start completion: # frozen_string_literal: true

module Coltrane
  module Theory
    # Allows the creation of chord progressions using standard notations.
    # Ex: Progression.new('I-IV-V', key: 'Am')
    class Progression
      extend NotableProgressions
      include Changes
      attr_reader :scale, :chords, :notation

      def self.find(*chords)
        chords
          .yield_self { |chords|
            next chords if chords[0].is_a?(Chord)
            chords.map {|c| Chord.new(name: c) }
      
    
      def self.find(*chords)
        chords
          .yield_self { |chords|
            next chords if chords[0].is_a?(Chord)
            chords.map {|c| Chord.new(name: c) }
          }
          .yield_self { |chords|
            NoteSet[*chords.map(&:root_note)]
            .yield_self { |root_notes|
              Scale.having_notes(*root_notes).strict_scales
            }
            .reduce([]) { |memo, scale|
              memo + [Progression.new(chords: chords, scale: scale)]
            }
          }
          .yield_self { |progressions| ProgressionSet.new(*progressions) }
      end