code: public com.google.api.ads.adwords.axis.v201809.cm.BidModifierSource getBidModifierSource() {
          return bidModifierSource;
      }
docs: Gets the bidModifierSource value for this AdGroupBidModifier.
  
  @return bidModifierSource   * Bid modifier source.
  <span class="constraint ReadOnly">This field is read
  only and will be ignored when sent to the API.</span>