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: timezone_period.rb
    path of file: ./repos/stackneveroverflow/vendor/bundle/ruby/2.3.0/gems/tzinfo-1.2.3/lib/tzinfo
    
    the code of the file until where you have to start completion: module TZInfo
  # A period of time in a timezone where the same offset from UTC applies.
  #
  # All the metho
    
    def initialize(start_transition, end_transition, offset = nil)
      @start_transition = start_transition
      @end_transition = end_transition
      
      if offset
        raise ArgumentError, 'Offset specified with transitions' if @start_transition || @end_transition
        @offset = offset
      else
        if @start_transition 
          @offset = @start_transition.offset
        elsif @end_transition
          @offset = @end_transition.previous_offset
        else
          raise ArgumentError, 'No offset specified and no transitions to determine it from'
        end