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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 expand_role(self, role):
 """Expand an IAM role name into an ARN. If the role is already in the form of an ARN, then the role is simply returned. Otherwise we retrieve the full ARN and return it. Args: role (str):
 An AWS IAM role (either name or full ARN). Returns: str: The corresponding AWS IAM role ARN. """

        if '/' in role:
            return role
        else:
            return self.boto_session.resource('iam').Role(role).arn