code: def _SetHeader(self, values):
      
      if self._values and len(values) != len(self._values):
        raise ValueError('Header values not equal to existing data width.')
      if not self._values:
        for _ in range(len(values)):
          self._values.append(None)
      self._keys = list(values)
      self._BuildIndex()
docs: Set the row's header from a list.