code: def to_dataframe(self):
          
          assert HAS_PANDAS, 'pandas is not installed.'
          df = pandas.DataFrame()
          for i in range(self.num_columns()):
              column_name = self.column_names()[i]
              df[column_name] = list(self[column_name])
              if len(df[column_name]) == 0:
                  df[column_name] = df[column_name].astype(self.column_types()[i])
          return df
docs: Convert this SFrame to pandas.DataFrame.
  
          This operation will construct a pandas.DataFrame in memory. Care must
          be taken when size of the returned object is big.
  
          Returns
          -------
          out : pandas.DataFrame
              The dataframe which contains all rows of SFrame