Adds an rdf value to the collection.

    Adds an rdf value to the collection. Does not require that the collection
    be locked.

    Args:
      rdf_value: The rdf value to add to the collection.
      timestamp: The timestamp (in microseconds) to store the rdf value at.
        Defaults to the current time.
      suffix: A 'fractional timestamp' suffix to reduce the chance of
        collisions. Defaults to a random number.
      mutation_pool: A MutationPool object to write to.

    Returns:
      The pair (timestamp, suffix) which identifies the value within the
      collection.

    Raises:
      ValueError: rdf_value has unexpected type.

def Add(self, rdf_value, timestamp=None, suffix=None, mutation_pool=None):
    """Adds an rdf value to the collection.

    Adds an rdf value to the collection. Does not require that the collection
    be locked.

    Args:
      rdf_value: The rdf value to add to the collection.
      timestamp: The timestamp (in microseconds) to store the rdf value at.
        Defaults to the current time.
      suffix: A 'fractional timestamp' suffix to reduce the chance of
        collisions. Defaults to a random number.
      mutation_pool: A MutationPool object to write to.

    Returns:
      The pair (timestamp, suffix) which identifies the value within the
      collection.

    Raises:
      ValueError: rdf_value has unexpected type.

    """
    return self.StaticAdd(
        self.collection_id,
        rdf_value,
        timestamp=timestamp,
        suffix=suffix,
        mutation_pool=mutation_pool)