code: public void setStartDateTime(com.google.api.ads.admanager.axis.v201811.DateTime startDateTime) {
          this.startDateTime = startDateTime;
      }
docs: Sets the startDateTime value for this DateTimeRange.
  
  @param startDateTime   * The start date time of this range. This field is optional and
  if it is not set then there is no
  lower bound on the date time range. If this field
  is not set then {@code endDateTime} must be
  specified.