Documentation to ezdxf
In DXF R12 an prior the HEADER section was optional, but since DXF R13 the HEADER section is mandatory. The overall structure is:
0 <<< Begin HEADER section SECTION 2 HEADER 9 $ACADVER <<< Header variable items go here 1 AC1009 ... 0 ENDSEC <<< End HEADER section
A header variable has a name defined by a
(9, Name) tag and following value tags.
DXF Reference: Header Variables