code: public BranchEvent addCustomDataProperty(String propertyName, String propertyValue) {
          try {
              this.customProperties.put(propertyName, propertyValue);
          } catch (JSONException e) {
              e.printStackTrace();
          }
          return this;
      }
docs: Adds a custom data property associated with this Branch Event
  
  @param propertyName  {@link String} Name of the custom property
  @param propertyValue {@link String} Value of the custom property
  @return This object for chaining builder methods