code: func (a *CompositeAggregationDateHistogramValuesSource) MissingBucket(missingBucket bool) *CompositeAggregationDateHistogramValuesSource {
  	a.missingBucket = &missingBucket
  	return a
  }
docs: // MissingBucket, if true, will create an explicit null bucket which represents
  // documents with missing values.