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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def get_activities(self, count=10, since=None, style='summary', limit=None):
 """Iterate over all activities, from newest to oldest. :param count: The number of results to retrieve per page. If set to ``None``, pagination is disabled. :param since: Return only activities since this date. Can be either a timestamp or a datetime object. :param style: The type of records to return. May be one of 'summary', 'briefs', 'ids', or 'extended'. :param limit: The maximum number of activities to return for the given query. """

        params = {}
        if since:
            params.update(fromDate=to_timestamp(since))
        parts = ['my', 'activities', 'search']
        if style != 'summary':
            parts.append(style)
        url = self._build_url(*parts)
        # TODO: return an Activity (or ActivitySummary?) class that can do
        # things like convert date and time fields to proper datetime objects
        return islice(self._iter(url, count, **params), limit)