How to use the apollo-language-server.isClientConfig function in apollo-language-server

if (flags.endpoint) {
      config.setDefaults({
        service: {
          endpoint: {
            url: flags.endpoint,
            headers: headersArrayToObject(flags.header),
            ...(flags.skipSSLValidation && { skipSSLValidation: true })
          }
        }
      });
    }

    // this can set a single or multiple local schema files
    if (flags.localSchemaFile) {
      const files = flags.localSchemaFile.split(",");
      if (isClientConfig(config)) {
        config.setDefaults({
          client: {
            service: {
              localSchemaFile: files
            }
          }
        });
      } else if (isServiceConfig(config)) {
        config.setDefaults({
          service: {
            localSchemaFile: files
          }
        });
      }
    }

if (flags.endpoint) {
      config.setDefaults({
        service: {
          endpoint: {
            url: flags.endpoint,
            headers: headersArrayToObject(flags.header),
            ...(flags.skipSSLValidation && { skipSSLValidation: true })
          }
        }
      });
    }

    // this can set a single or multiple local schema files
    if (flags.localSchemaFile) {
      const files = flags.localSchemaFile.split(",");
      if (isClientConfig(config)) {
        config.setDefaults({
          client: {
            service: {
              localSchemaFile: files
            }
          }
        });
      } else if (isServiceConfig(config)) {
        config.setDefaults({
          service: {
            localSchemaFile: files
          }
        });
      }
    }

: URI.file(parse(configPath).dir);

    const clientIdentity = {
      name: "Apollo CLI",
      version,
      referenceID
    };

    if (isServiceConfig(config)) {
      this.project = new GraphQLServiceProject({
        config,
        loadingHandler,
        rootURI,
        clientIdentity
      });
    } else if (isClientConfig(config)) {
      this.project = new GraphQLClientProject({
        config,
        loadingHandler,
        rootURI,
        clientIdentity
      });
    } else {
      throw new Error(
        "Unable to resolve project type. Please add either a client or service config. For more information, please refer to https://bit.ly/2ByILPj"
      );
    }

    this.ctx.project = this.project;
  }