code: def get_series_names(self, column_indices = [], column_names = []):
          '''Returns the series' names corresponding to column_indices and column_names.
             "names" here are:
                - strings for single-indexed dataframes; or
                - tuples for multi-indexed dataframes.
  
             If both parameters are empty then all column names are returned.
          '''
          n = []
          if not column_indices and not column_names:
              for k, v in sorted(self.series_names.iteritems()):
                  # Iterate by index to preserve document order
                  if v != self.reference_series:
                      n.append(k)
          else:
              s = set([self.series_names[x] for x in column_indices])
              t = set([self.series_index[x] for x in column_names])
              n = sorted(s.union(t))
          assert(n)
          return [self.series_names[x] for x in nf get_series_names(self, column_indices = [], column_names = []):
          '''Returns the series' names corresponding to column_indices and column_names.
             "names" here are:
                - strings for single-indexed dataframes; or
                - tuples for multi-indexed dataframes.
  
             If both parameters are empty then all column names are returned.
          '''
          n = []
          if not column_indices and not column_names:
              for k, v in sorted(self.series_names.iteritems()):
                  # Iterate by index to preserve document order
                  if v != self.reference_series:
                      n.append(k)
          else:
              s = set([self.series_names[x] for x in column_indices])
              t = set([self.series_index[x] for x in column_names])
              n = sorted(s.union(t))
          assert(n)
          return [self.series_names[x] for x in n]
docs: Returns the series' names corresponding to column_indices and column_names.
             "names" here are:
                - strings for single-indexed dataframes; or
                - tuples for multi-indexed dataframes.
  
             If both parameters are empty then all column names are returned.