@tornado.gen.coroutine<EOL>def get_instance_mem_histogram(cluster, environ, topology, instance, role=None):
params = dict(<EOL>cluster=cluster,<EOL>environ=environ,<EOL>topology=topology,<EOL>instance=instance)<EOL>if role is not None:<EOL><INDENT>params['<STR_LIT>'] = role<EOL><DEDENT>request_url = tornado.httputil.url_concat(<EOL>create_url(HISTOGRAM_URL_FMT), params)<EOL>raise tornado.gen.Return((yield fetch_url_as_json(request_url)))<EOL>
:param cluster:
:param environ:
:param topology:
:param instance:
:param role:
:return: