Finds keys in a hash that are not strings

detect_bad_keys.rb

def detect_bad_keys(obj, parent_path)
  result = []
  case obj
  when Hash
    obj.each do |key, value|
      if key.is_a?(String)
        result.concat(detect_bad_keys(value, [*parent_path, key]))
      else
        result.push([*parent_path, key])
      end
    end
  when Array
    obj.each_with_index do |value, key|      
      result.concat(detect_bad_keys(value, [*parent_path, key]))      
    end
  end
  result
end