'Initialize the widget, called when configuring an available
widget for the dashboard.
@param label: a label for this widget type, used in the widget
selector in the configuration GUI; if left empty,
then the widget type will not appear in the selector
@param defaults: the default configuration for this widget
@param on_create_agent: callback, invoked when an agent is created
for this widget:
- on_create_agent(agent, context)
@param **options: type-specific options'

def __init__(self, label=None, defaults=None, on_create_agent=None, **options):

    self.label = label
    if (defaults is None):
        defaults = {}
    self.defaults = defaults
    self.options = options
    self.on_create_agent = on_create_agent
    self.agents = {}
    self.script_loaded = False
