code: def get_pmid(doc_id):
      
      url_pmid = 'https://www.ebi.ac.uk/chembl/api/data/document.json'
      params = {'document_chembl_id': doc_id}
      res = requests.get(url_pmid, params=params)
      js = res.json()
      pmid = str(js['documents'][0]['pubmed_id'])
      return pmid
docs: Get PMID from document_chembl_id
  
      Parameters
      ----------
      doc_id : str
  
      Returns
      -------
      pmid : str