Fix: faulty encoding without faithfulness

Author: anujthak

gap/io.gi

@@ -2283,15 +2283,6 @@ function(D)
   # matrix, and appends a '&' to the start.  The old '+' format can be read by
   # DigraphFromDigraph6String, but can no longer be written by this function.
 
-  if IsMultiDigraph(D) then
-    if IsSymmetricDigraph(D) then
-      ErrorNoReturn("the argument <D> must not have multiple edges ",
-                  "consider encoding in Sparse6 or Disparse6, ");
-    fi;
-    ErrorNoReturn("the argument <D> must not have multiple edges ",
-                  "consider encoding in Disparse6, ");
-  fi;
-
   list := [];
   adj := OutNeighbours(D);
   n := Length(DigraphVertices(D));
@@ -2357,13 +2348,6 @@ InstallMethod(Sparse6String, "for a digraph by out-neighbours",
 function(D)
   local list, n, lenlist, adj, nredges, k, blist, v, nextbit, i, j,
         bitstopad, pos, block;
-  if not IsSymmetricDigraph(D) then
-    if IsMultiDigraph(D) then
-      ErrorNoReturn("the argument <D> must be a symmetric digraph consider encoding in Disparse6,");
-    fi;
-    else
-      ErrorNoReturn("the argument <D> must be a symmetric digraph consider encoding in Digraph6 or Disparse6,");
-  fi;
 
   if not IsSymmetricDigraph(D) then
     if IsMultiDigraph(D) then

tst/standard/io.tst

@@ -546,7 +546,8 @@ Error, the 2nd argument <s> is not a valid disparse6 string,
 
 #  Special format characters
 gap> Sparse6String(ChainDigraph(3));
-Error, the argument <D> must be a symmetric digraph,
+Error, the argument <D> must be a symmetric digraph consider encoding in Digra\
+ph6 or Disparse6,
 gap> Sparse6String(CompleteDigraph(1));
 ":@"
 gap> gr := Digraph([[1], []]);;