Get the ledger ID of the object

        Example:
        source_id = 'foobar123'
        schema_name = 'Schema Name'
        payment_handle = 0
        credential_def1 = await CredentialDef.create(source_id, name, schema_id, payment_handle)
        assert await credential_def.get_cred_def_id() == '2hoqvcwupRTUNkXn6ArYzs:3:CL:2471'
        :return: ID string

async def get_cred_def_id(self):
        """
        Get the ledger ID of the object

        Example:
        source_id = 'foobar123'
        schema_name = 'Schema Name'
        payment_handle = 0
        credential_def1 = await CredentialDef.create(source_id, name, schema_id, payment_handle)
        assert await credential_def.get_cred_def_id() == '2hoqvcwupRTUNkXn6ArYzs:3:CL:2471'
        :return: ID string
        """
        cb = create_cb(CFUNCTYPE(None, c_uint32, c_uint32, c_char_p))
        c_handle = c_uint32(self.handle)
        cred_def_id = await do_call('vcx_credentialdef_get_cred_def_id', c_handle, cb)
        return cred_def_id .decode()