Returns all flow objects.

def ReadAllFlowObjects(self,
                         client_id = None,
                         min_create_time = None,
                         max_create_time = None,
                         include_child_flows = True,
                         cursor=None):
    """Returns all flow objects."""
    conditions = []
    args = []

    if client_id is not None:
      conditions.append("client_id = %s")
      args.append(db_utils.ClientIDToInt(client_id))

    if min_create_time is not None:
      conditions.append("timestamp >= FROM_UNIXTIME(%s)")
      args.append(mysql_utils.RDFDatetimeToTimestamp(min_create_time))

    if max_create_time is not None:
      conditions.append("timestamp <= FROM_UNIXTIME(%s)")
      args.append(mysql_utils.RDFDatetimeToTimestamp(max_create_time))

    if not include_child_flows:
      conditions.append("parent_flow_id IS NULL")

    query = "SELECT {} FROM flows".format(self.FLOW_DB_FIELDS)
    if conditions:
      query += " WHERE " + " AND ".join(conditions)

    cursor.execute(query, args)
    return [self._FlowObjectFromRow(row) for row in cursor.fetchall()]