Note: google_bigtable_instance_iam_policy cannot be used in conjunction with google_bigtable_instance_iam_binding and google_bigtable_instance_iam_member or they will fight over what your policy should be. In addition, be careful not to accidentally unset ownership of the instance as google_bigtable_instance_iam_policy replaces the entire policy.
Note: google_bigtable_instance_iam_binding resources can be used in conjunction with google_bigtable_instance_iam_member resources only if they do not grant privilege to the same role.
See https://www.terraform.io/docs/providers/google/r/bigtable_instance_iam.html