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: belongs_to.rb
    path of file: ./repos/lol_dba/lib/lol_dba/index_finding
    
    the code of the file until where you have to start completion: module LolDba
  class BelongsTo < RelationInspector
    def relation_columns
      if reflection_options.options[:polymorphic]
        name = reflect
    
    def relation_columns
      if reflection_options.options[:polymorphic]
        name = reflection_options.name
        poly_type = "#{name}_type"
        poly_id = "#{name}_id"
        [poly_type, poly_id].sort
      else
        foreign_key = non_polymorphic_fk

        # not a clue why rails 4.1+ creates this left_side_id thing
        foreign_key == 'left_side_id' ? nil : foreign_key.to_s
      end