code: def get_pcid(mesh_id):
      
      url_mesh2pcid = 'http://eutils.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi'
      params = {'dbfrom': 'mesh', 'id': mesh_id,
                'db': 'pccompound', 'retmode': 'JSON'}
      r = requests.get(url_mesh2pcid, params=params)
      res = r.json()
      pcid = res['linksets'][0]['linksetdbs'][0]['links'][0]
      return pcid
docs: Get PC ID from MESH ID
  
      Parameters
      ----------
      mesh : str
  
      Returns
      -------
      pcid : str