Set the value into the data store.

def Set(self,
          subject,
          attribute,
          value,
          timestamp=None,
          replace=True,
          sync=True):
    """Set the value into the data store."""
    subject = utils.SmartUnicode(subject)

    _ = sync
    attribute = utils.SmartUnicode(attribute)

    if timestamp is None or timestamp == self.NEWEST_TIMESTAMP:
      timestamp = time.time() * 1000000

    if subject not in self.subjects:
      self.subjects[subject] = {}

    if replace or attribute not in self.subjects[subject]:
      self.subjects[subject][attribute] = []

    encoded_value = self._value_converter.Encode(attribute, value)
    self.subjects[subject][attribute].append([encoded_value, int(timestamp)])
    self.subjects[subject][attribute].sort(key=lambda x: x[1])