code: def WriteRow(self, values):
      
      precondition.AssertDictType(values, text, text)
  
      row = []
      for column in self._columns:
        try:
          value = values[column]
        except KeyError:
          raise ValueError("Row does not contain required column `%s`" % column)
  
        row.append(value)
  
      self._writer.WriteRow(row)
docs: Writes a single row to the underlying buffer.
  
      Args:
        values: A dictionary mapping column names to values to be inserted into
          the CSV output.