code: func (p FieldValues) ColumnKeys() []string {
  	if !p.HasColumnKeys() {
  		return nil
  	}
  	other := make([]string, len(p))
  	for i := range p {
  		other[i] = p[i].ColumnKey
  	}
  	return other
  }
docs: // ColumnKeys returns a slice of all the column keys.