GetDefinitionMetrics.
        [Preview API] Gets build metrics for a definition.
        :param str project: Project ID or project name
        :param int definition_id: The ID of the definition.
        :param datetime min_metrics_time: The date from which to calculate metrics.
        :rtype: [BuildMetric]

def get_definition_metrics(self, project, definition_id, min_metrics_time=None):
        """GetDefinitionMetrics.
        [Preview API] Gets build metrics for a definition.
        :param str project: Project ID or project name
        :param int definition_id: The ID of the definition.
        :param datetime min_metrics_time: The date from which to calculate metrics.
        :rtype: [BuildMetric]
        """
        route_values = {}
        if project is not None:
            route_values['project'] = self._serialize.url('project', project, 'str')
        if definition_id is not None:
            route_values['definitionId'] = self._serialize.url('definition_id', definition_id, 'int')
        query_parameters = {}
        if min_metrics_time is not None:
            query_parameters['minMetricsTime'] = self._serialize.query('min_metrics_time', min_metrics_time, 'iso-8601')
        response = self._send(http_method='GET',
                              location_id='d973b939-0ce0-4fec-91d8-da3940fa1827',
                              version='5.0-preview.1',
                              route_values=route_values,
                              query_parameters=query_parameters)
        return self._deserialize('[BuildMetric]', self._unwrap_collection(response))