export: dictionaries are now formatted like in the original OBITools

when exporting in tabular format and tuple formatting is cleaner

python/obitools3/format/tab.pyx

@@ -3,7 +3,7 @@
 cimport cython
 from obitools3.dms.view.view cimport Line
 from obitools3.utils cimport bytes2str_object, str2bytes, tobytes
-from obitools3.dms.column.column cimport Column_line
+from obitools3.dms.column.column cimport Column_line, Column_multi_elts
 
 
 cdef class TabFormat:
@@ -25,19 +25,29 @@ cdef class TabFormat:
         for k in self.tags:
             
             if self.header and self.first_line:
-                value = tobytes(k)
+                if isinstance(data.view[k], Column_multi_elts):
+                    for k2 in data.view[k].keys():
+                        line.append(tobytes(k)+b':'+tobytes(k2))
+                else:
+                    line.append(tobytes(k))
             else:
                 value = data[k]
-                if value is not None:
-                    if type(value) == Column_line:
-                        value = value.bytes()
+                if isinstance(data.view[k], Column_multi_elts):
+                    if value is None:  # all keys at None
+                        for k2 in data.view[k].keys(): # TODO could be much more efficient
+                            line.append(self.NAString)
                     else:
-                        value = str2bytes(str(bytes2str_object(value))) # genius programming
-                if value is None:
-                    value = self.NAString
-            
-            line.append(value)
-      	
+                        for k2 in data.view[k].keys(): # TODO could be much more efficient
+                            if value[k2] is not None:
+                                line.append(str2bytes(str(bytes2str_object(value[k2]))))  # genius programming
+                            else:
+                                line.append(self.NAString)
+                else:
+                    if value is not None:
+                        line.append(str2bytes(str(bytes2str_object(value))))
+                    else:
+                        line.append(self.NAString)
+                  	
         if self.first_line:
             self.first_line = False