code: func ExtractVariables(configDict map[string]interface{}, pattern *regexp.Regexp) map[string]string {
  	if pattern == nil {
  		pattern = defaultPattern
  	}
  	return recurseExtract(configDict, pattern)
  }
docs: // ExtractVariables returns a map of all the variables defined in the specified
  // composefile (dict representation) and their default value if any.