API client is mainly responible for making the HTTP call to the API backend.
 /// <summary>
 /// Initializes a new instance of the <see cref="CatalogModuleApi"/> class.
 /// </summary>
 /// <param name="apiClient"> an instance of ApiClient (optional)</param>
 /// <returns></returns>
 public CatalogModuleApi(ApiClient apiClient = null)
 {
     if (apiClient == null) // use the default one in Configuration
         this.ApiClient = Configuration.DefaultApiClient; 
     else
         this.ApiClient = apiClient;
 }
 /// <summary>
 /// Initializes a new instance of the <see cref="CustomerManagementModuleApi"/> class.
 /// </summary>
 /// <param name="apiClient"> an instance of ApiClient (optional)</param>
 /// <returns></returns>
 public CustomerManagementModuleApi(ApiClient apiClient = null)
 {
     if (apiClient == null) // use the default one in Configuration
         this.ApiClient = Configuration.DefaultApiClient; 
     else
         this.ApiClient = apiClient;
 }