There seems to be a bug in the sparse6 string generator.
sage: G=graphs.EllinghamHorton78Graph()
sage: G.sparse6_string()
':~?@M_GEA_w?C`WGEaOOGaWWI_OmGBGKL`w}OcXINCxQGCPUWCp]WdPeOEh[Zc`q^Fh}_gXwagyAfGaYfhAa^IYEgIyqlji}ojREqfa{rlbCtljKvjbatMYWv_Jq|hBy{hSAdn{M
*\\*OCRAeRtEa_wVlSHBhagjkBgzpCY}OSr'
It is not a bug. Python displays \ as \\
sage: '\\'
'\\'
sage: len('\\')
1
What is wrong is that you should not copy paste this string to another
software but instead do
sage: print G.sparse6_string()
:~?@M_GEA_w?C`WGEaOOGaWWI_OmGBGKL`w}OcXINCxQGCPUWCp]WdPeOEh[Zc`q^Fh}_gXwagyAfGaYfhAa^IYEgIyq
