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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_keys(self, label=None):
 """Lists all SSH keys on the account. :param string label: Filter list based on SSH key label :returns: A list of dictionaries with information about each key """

        _filter = utils.NestedDict({})
        if label:
            _filter['sshKeys']['label'] = utils.query_filter(label)

        return self.client['Account'].getSshKeys(filter=_filter.to_dict())