code: def find_by_content_type(content_type):
      
      for format in FORMATS:
          if content_type in format.content_types:
              return format
  
      raise UnknownFormat('No format found with content type "%s"' % content_type)
docs: Find and return a format by content type.
  
      :param content_type: A string describing the internet media type of the format.