How to use the pdpyras.PDSession function in pdpyras

def __init__(self, api_key, name=None):
        """
        Basic constructor for API sessions.

        :param api_key:
            The API credential to use.
        :param name:
            Identifying label for the session to use in log messages
        """
        self.parent = super(PDSession, self)
        self.parent.__init__()
        self.api_key = api_key
        if isinstance(name, string_types) and name:
            my_name = name
        else:
            my_name = self.trunc_key
        self.log = logging.getLogger('pdpyras.%s(%s)'%(
            self.__class__.__name__, my_name))
        self.retry = {}

raise ValueError(local+" must be a dict")
        event = {'payload': {'summary':summary, 'source':source,
            'severity':severity}}
        if type(payload) is dict:
            event['payload'].update(payload)
        if type(custom_details) is dict:
            details = event.setdefault('payload', {}).get('custom_details', {})
            details.update(custom_details)
            event['payload']['custom_details'] = details
        if images:
            event['images'] = images
        if links:
            event['links'] = links
        return self.send_event('trigger', dedup_key=dedup_key, **event)

class APISession(PDSession):
    """
    Reusable PagerDuty REST API session objects for making API requests.

    Includes some convenience functions as well, i.e. :attr:`rget`, :attr:`find`
    and :attr:`iter_all`, to eliminate some repetitive tasks associated with
    making API calls.

    Inherits from :class:`PDSession`.

    :param api_key:
        REST API access token to use for HTTP requests
    :param name:
        Optional name identifier for logging. If unspecified or ``None``, it
        will be the last four characters of the REST API token.
    :param default_from:
        Email address of a valid PagerDuty user to use in API requests by

    @property
    def trunc_key(self):
        """Truncated key for secure display/identification purposes."""
        return last_4(self.api_key)

    @property
    def user_agent(self):
        return 'pdpyras/%s python-requests/%s Python/%d.%d'%(
            __version__,
            requests.__version__,
            sys.version_info.major,
            sys.version_info.minor
        )

class EventsAPISession(PDSession):

    """
    Session class for submitting events to the PagerDuty v2 Events API.

    Provides methods for submitting events to the Events API.

    Inherits from :class:`PDSession`.
    """

    permitted_methods = ('POST',)

    url = "https://events.pagerduty.com"

    @property
    def auth_header(self):
        return {'X-Routing-Key': self.api_key}