@Input
  @Optional
  public Map<String, String> getEnvironment() {
    if (System.getProperty(PropertyNames.DOCKER_CLIENT_ENVIRONMENT) != null) {
      return ConfigurationPropertyValidator.parseMapProperty(
          System.getProperty(PropertyNames.DOCKER_CLIENT_ENVIRONMENT));
    }
    return environment;
  }
Object that configures the Docker executable and the additional environment variables to use when
executing the executable.
jib-gradle-plugin/src/main/java/com/google/cloud/tools/jib/gradle/DockerClientParameters.java