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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 update_by_config(self, config_dict):
 """ Update policies set by the config dictionary. Expect the policy_enabling_map structure to be (represented by YAML):
 - PolicyFoo: enabled: True - PolicyBar: enabled: False additional_field: 'is_ok' """

        policy_enabling_map = self._get_enabling_map(config_dict)
        self.enabled_policies = []

        for policy_name, is_policy_enabled in policy_enabling_map.items():
            if not self._is_policy_exists(policy_name):
                self._warn_unexistent_policy(policy_name)
                continue

            if is_policy_enabled:
                enabled_policy = self._get_policy(policy_name)
                self.enabled_policies.append(enabled_policy)