instance method tables_in_hash

# File activerecord/lib/active_record/associations.rb, line 1711
        def tables_in_hash(hash)
          return [] if hash.blank?
          tables = hash.map do |key, value|
            if value.is_a?(Hash)
              key.to_s
            else
              tables_in_string(key) if key.is_a?(String)
            end
          end
          tables.flatten.compact
        end