code: def get_id_count(search_term):
      
      params = {'term': search_term,
                'rettype': 'count',
                'db': 'pubmed'}
      tree = send_request(pubmed_search, params)
      if tree is None:
          return None
      else:
          count = tree.getchildren()[0].text
          return int(count)
docs: Get the number of citations in Pubmed for a search query.
  
      Parameters
      ----------
      search_term : str
          A term for which the PubMed search should be performed.
  
      Returns
      -------
      int or None
          The number of citations for the query, or None if the query fails.