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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 list_entities_for_policy(policy_name, path_prefix=None, entity_filter=None,
                  region=None, key=None, keyid=None, profile=None):
    '''
    List entities that a policy is attached to.

    CLI Example:

    .. code-block:: bash

        salt myminion boto_iam.list_entities_for_policy mypolicy
    '''
    conn = _get_conn(region=region, key=key, keyid=keyid, profile=profile)
    retries = 30

    params = {}
    for arg in ('path_prefix', 'entity_filter'):
        if locals()[arg] is not None:
            params[arg] = locals()[arg]

    policy_arn = _get_policy_arn(policy_name, region, key, keyid, profile)
    while retries:
        try:
            allret = {
              'policy_groups': [],
              'policy_users': [],
              'policy_roles': [],
            }
            for ret in __utils__['boto.paged_call'](conn.list_entities_for_policy, policy_arn=policy_arn, **params):
                for k, v in six.iteritems(allret):
                    v.extend(ret.get('list_entities_for_policy_response', {}).get('list_entities_for_policy_result', {}).get(k))
            return allret
        except boto.exception.BotoServerError as e:
            if e.error_code == 'Throttling':
                log.debug("Throttled by AWS API, will retry in 5 seconds...")
                time.sleep(5)
                retries -= 1
                continue
            log.error('Failed to list entities for IAM policy %s: %s', policy_name, e.message)
            return {}
    return {}