'Init the attribute
name: Attribute name (string)
description: Attribute human reading description (string)
history_max_size: Maximum size of the history list (default is no limit)
History is stored as a list for tuple: [(date, value), ...]'

def __init__(self, name, description='', history_max_size=None):

    self._name = name
    self._description = description
    self._value = None
    self._history_max_size = history_max_size
    self._history = []
