code: def get_hgnc_name(hgnc_id):
      
      try:
          hgnc_name = hgnc_names[hgnc_id]
      except KeyError:
          xml_tree = get_hgnc_entry(hgnc_id)
          if xml_tree is None:
              return None
          hgnc_name_tag =\
              xml_tree.find("result/doc/str[@name='symbol']")
          if hgnc_name_tag is None:
              return None
          hgnc_name = hgnc_name_tag.text.strip()
      return hgnc_name
docs: Return the HGNC symbol corresponding to the given HGNC ID.
  
      Parameters
      ----------
      hgnc_id : str
          The HGNC ID to be converted.
  
      Returns
      -------
      hgnc_name : str
          The HGNC symbol corresponding to the given HGNC ID.