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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 valid_kdf(self, kdf):
 """Determine whether a KDFSuite can be used with this EncryptionSuite. :param kdf: KDFSuite to evaluate :type kdf: aws_encryption_sdk.identifiers.KDFSuite :rtype: bool """

        if kdf.input_length is None:
            return True

        if self.data_key_length > kdf.input_length(self):
            raise InvalidAlgorithmError(
                "Invalid Algorithm definition: data_key_len must not be greater than kdf_input_len"
            )

        return True