code: def extract(self, *args):
          
          self.time = np.loadtxt(self.abspath,
                                 skiprows=self._attributes['data_idx']+1,
                                 unpack=True, usecols=(0,))
          for variable_idx in args:
              data = np.loadtxt(self.abspath,
                                skiprows=self._attributes['data_idx']+1,
                                unpack=True,
                                usecols=(variable_idx,))
              with open(self.abspath) as fobj:
                  for idx, line in enumerate(fobj):
                      if idx == 1 + variable_idx+self._attributes['CATALOG']:
                          try:
                              self.data[variable_idx] = data[:len(self.time)]
                          except TypeError:
                              self.data[variable_idx] = data.base
                          self.label[variable_idx] = line.replace("\'",
                                                                  '').replace("\n",
                                                                              "")
                          break
docs: Extract a specific variable