code: def download(url, params=None, accept="xml", **kwds):
      
      # Value check
      accepted = ("json", "xml", "atom+xml")
      if accept.lower() not in accepted:
          raise ValueError('accept parameter must be one of ' +
                           ', '.join(accepted))
      # Get credentials
      key = config.get('Authentication', 'APIKey')
      header = {'X-ELS-APIKey': key}
      if config.has_option('Authentication', 'InstToken'):
          token = config.get('Authentication', 'InstToken')
          header.update({'X-ELS-APIKey': key, 'X-ELS-Insttoken': token})
      header.update({'Accept': 'application/{}'.format(accept)})
      # Perform request
      params.update(**kwds)
      resp = requests.get(url, headers=header, params=params)
      # Raise error if necessary
      try:
          reason = resp.reason.upper() + " for url: " + url
          raise errors[resp.status_code](reason)
      except KeyError:  # Exception not specified in scopus
          resp.raise_for_status()  # Will pass when everything is ok
      return resp
docs: Helper function to download a file and return its content.
  
      Parameters
      ----------
      url : string
          The URL to be parsed.
  
      params : dict (optional)
          Dictionary containing query parameters.  For required keys
          and accepted values see e.g.
          https://api.elsevier.com/documentation/AuthorRetrievalAPI.wadl
  
      accept : str (optional, default=xml)
          mime type of the file to be downloaded.  Accepted values are json,
          atom+xml, xml.
  
      kwds : key-value parings, optional
          Keywords passed on to as query parameters.  Must contain fields
          and values specified in the respective API specification.
  
      Raises
      ------
      ScopusHtmlError
          If the status of the response is not ok.
  
      ValueError
          If the accept parameter is not one of the accepted values.
  
      Returns
      -------
      resp : byte-like object
          The content of the file, which needs to be serialized.