docs: def parse_meta(self, selected_meta_data):
          """
          Parses all of the metadata files
          :param selected_meta_data: if specified then only the columns that are contained here are going to be parsed
          :return:
          """
          # reads all meta data files
          files = self._get_files("meta", self.path)
          df = pd.DataFrame()
          print("Parsing the metadata files...")
          for f in tqdm(files):
              data = self.parse_single_meta(f, selected_meta_data)
              if data is not None:
                  df = pd.concat([df, data], axis=0)
          df.index = df['sample']
          #
          # df = df.drop('sample', 1)  # 1 for the columns
          return df