code: def grep(filename, tag, firstOccurrence=False):
      
      import re
  
      try:
          afile = open(filename, "r")
      except:
          print("Error in utils.grep(): cannot open file", filename)
          exit()
      content = None
      for line in afile:
          if re.search(tag, line):
              content = line.split()
              if firstOccurrence:
                  break
      if content:
          if len(content) == 2:
              content = content[1]
          else:
              content = content[1:]
      afile.close()
      return content
docs: Greps the line that starts with a specific `tag` string from inside a file.