code: def get_letters( word ):
      
      ta_letters = list()
      not_empty = False
      WLEN,idx = len(word),0
      while (idx < WLEN):
          c = word[idx]
          #print(idx,hex(ord(c)),len(ta_letters))
          if c in uyir_letter_set or c == ayudha_letter:
              ta_letters.append(c)
              not_empty = True
          elif c in grantha_agaram_set:
              ta_letters.append(c)
              not_empty = True
          elif c in accent_symbol_set:
              if not not_empty:
                  # odd situation
                  ta_letters.append(c)
                  not_empty = True
              else:
                  #print("Merge/accent")
                  ta_letters[-1] += c
          else:
              if ord(c) < 256 or not (is_tamil_unicode(c)):
                  ta_letters.append( c )
              else:
                  if not_empty:
                      #print("Merge/??")
                      ta_letters[-1]+= c
                  else:
                      ta_letters.append(c)
                      not_empty = True
          idx = idx + 1
      return ta_letters
docs: splits the word into a character-list of tamil/english
      characters present in the stream