code: func (e *RawV4Event) FixedLengthData() []byte {
  	begin := sizeOfBasicV4EventHeader + e.extraHeadersSize
  	end := sizeOfBasicV4EventHeader + e.extraHeadersSize + e.fixedLengthDataSize
  	return e.data[begin:end]
  }
docs: // RawV4Event's FixedLengthData returns the fixed legnth data associated to the
  // event.  NOTE: by default, the fixed-length data's size is not set and this
  // returns an empty byte slice.  Use SetFixedLengthDataSize to specify the
  // length.