code: def _parse_metadatas(self, text_lines):
          
          if not text_lines:
              return {}
          expr_metadata = re.compile(r'^#\+([a-zA-Z]+):(.*)')
          return {
              expr_metadata.match(line).group(1).lower()
              : expr_metadata.match(line).group(2).strip()
              for line in text_lines
          }
docs: From a given Org text, return the metadatas 
          Keyword Arguments:
          text_lines -- A list, each item is a line of the texte
          Return:
          A dict containing metadatas