docs: def return_net(word,word_net,depth=1):
      '''Creates a list of unique words that are at a provided depth from root word.
  
      @Args:
      --
      word :      root word from which the linked words should be returned.
      word_net :  word network (dictionary of word instances)to be refered in this process.
      depth :     depth to which this process must traverse and return words.
  
      @return:
      ---
      res :   List of words that are within a certain depth from root word in network.
  
      '''
      if depth<1: raise Exception(TAG+"Degree value error.range(1,~)")
      if depth==1:
          return list(word_net[word].frwrd_links)
      elif depth>1:
          words  = word_net[word].frwrd_links
          res=[]
          for w in words: res.extend(return_net(w,word_net,depth=depth-1))
          return list(set(res))