backwardSearch 
  fun backwardSearch(str: String, flags: TextSearchFlags, matchStart: TextIter?, matchEnd: TextIter?, limit: TextIter? = null): Boolean(source)
Same as method@Gtk.TextIter.forward_search, but moves backward.
Return
whether a match was found
Parameters
str
search string
flags
bitmask of flags affecting the search
matchStart 
return location for start of match
matchEnd 
return location for end of match
limit
location of last possible @match_start, or null for start of buffer