code: def process_url(o):
      """
      The function is used to process the spoken form of every URL in an example.
      E.g., "dot h_letter  _letter t_letter  _letter m_letter  _letter l_letter" ->
            "dot h t m l"
      Args:
          o: The expected outputs for the spoken form
      Return:
          o: The outputs for the spoken form with preprocessed URLs.
      """
  
      def flatten(l):
          """flatten a list of lists"""
          return [item for sublist in l for item in sublist]
  
      if o != "<self>" and "_letter" in o:
          o_tokens = o.split(" ")
          all_spans, cur_span = [], []
          for j in range(len(o_tokens)):
              if len(o_tokens[j]) == 0:
                  continue
              if o_tokens[j] == "_letter":
                  all_spans.append(cur_span)
                  all_spans.append([" "])
                  cur_span = []
              else:
                  o_tokens[j] = o_tokens[j].replace("_letter", "")
                  cur_span.append(o_tokens[j])
          if len(cur_span) > 0:
              all_spans.append(cur_span)
          o_tokens = flatten(all_spans)
  
          o = ""
          for o_token in o_tokens:
              if len(o_token) > 1:
                  o += " " + o_token + " "
              else:
                  o += o_token
          o = o.strip()
          o_tokens = processor.tokenize(o).split()
          o = " ".join(o_tokens)
  
      return o
  
file_path: NeMo/examples/nlp/duplex_text_normalization/data/en/data_preprocessing.py
imports: import os
  from argparse import ArgumentParser
  import inflect
  import regex
  from tqdm import tqdm
  from nemo.collections.common.tokenizers.moses_tokenizers import MosesProcessor
  from nemo.collections.nlp.data.text_normalization.constants import EN_GREEK_TO_SPOKEN
  from nemo.collections.nlp.data.text_normalization.utils import add_space_around_dash, convert_fraction, convert_superscript
  from nemo.utils import logging
label_desc: Use image node_id 1 for calling a global function with example usage: process_url(o) and returns: o, unknown