docs: def read_requirements(req_file):
      """Reads a requirements file.
  
      Args:
          req_file (str): Filename of requirements file
      """
      items = list(parse_requirements(req_file, session={}))
      result = []
  
      for item in items:
          # Get line number from item
          line_number = item.comes_from.split(req_file + ' (line ')[1][:-1]
          if item.req:
              item.req.marker = item.markers
              result.append((item.req, line_number))
          else:
              result.append((item, line_number))
  
      return result