code: def process_header(self, header):
          
          metadata = {}
          for line in header.split("\n"):
              line = line.strip()
              for tag in self.header_tags:
                  tag_text = "{}:".format(tag)
                  if line.lower().startswith(tag_text):
                      metadata[tag] = line[len(tag_text) + 1 :].strip()
  
          return metadata
docs: Parse the header for additional metadata.
  
          Parameters
          ----------
          header : str
              All the lines in the header.
  
          Returns
          -------
          dict
              The metadata in the header.