 a format specification to print.  We can define these methods Before_invoice and After_invoice because we have sorted on this field.  In our Before_invoice we return a format for the header portion of the report. This is simply a Vert container with a format for each item we want to print on the header.  We specified the format for invoice, but notice that just the field name was used for customer.  This means the format will be retrieved from the datadict entry for the field (This would be defined as Fiel