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: filter.rb
    path of file: ./repos/oso/languages/ruby/lib/oso/polar/data
    
    the code of the file until where you have to start completion: # frozen_string_literal: true

module Oso
  module Polar
    # Data filtering interface for Ruby
    module Data
      # Abstract data filter used by the Adapter API.
      class Filter
        attr_reader :model, :re
    
          def self.parse_side(polar, side)
            key = side.keys.first
            val = side[key]
            case key
            when 'Field'
              Projection.new(polar.name_to_class(val[0]), val[1])
            when 'Immediate'
              polar.host.to_ruby('value' => [[val.keys.first, val.values.first]])
            else
              raise key
            end