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**Description**

From Cloud Bigtable [documentation](https://cloud.google.com/bigtable/docs/replication-overview#how-it-works)
> Cloud Bigtable supports up to 4 replicated clusters located in Google Cloud zones where Cloud Bigtable is available.
Currently Bigtable hook and operator only support creating one replicated cluster. It would be better to add support for creating multiple replicated clusters

**Use case / motivation**

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Supporting multiple replicated clusters will be handy. It will be helpful to increase the availability and durability of the data by copying it across multiple regions or multiple zones within the same region.


airflow/providers/google/cloud/operators/bigtable.py
See https://cloud.google.com/bigtable/docs/locations for more details.
    :type project_id: str
    :param project_id: Optional, the ID of the GCP project.  If set to None or missing,
            the default project_id from the GCP connection is used.
    :type replica_cluster_id: str
    :param replica_cluster_id: (optional) The ID for replica cluster for the new instance.
    :type replica_cluster_zone: str
    :param replica_cluster_zone: (optional)  The zone for replica cluster.
    :type instance_type: enum.IntEnum
    :param instance_type: (optional) The type of the instance.
    :type instance_display_name: str
    :param instance_display_name: (optional) Human-readable name of the instance. Defaults
        to ``instance_id``.
    :type instance_labels: dict
    :param instance_labels: (optional) Dictionary of labels to associate
        with the instance.
    :type cluster_nodes: int
    :param cluster_nodes: (optional) Number of nodes for cluster.
    :type cluster_storage_type: enum.IntEnum
    :param cluster_storage_type: (optional) The type of storage.
    :type timeout: int
    :param timeout: (optional) timeout (in seconds) for instance creation.
                    If None is not specified, Operator will wait indefinitely.
    :param gcp_conn_id: The connection ID to use to connect to Google Cloud Platform.
    :type gcp_conn_id: str
    """
    REQUIRED_ATTRIBUTES: Iterable[str] = ('instance_id', 'main_cluster_id', 'main_cluster_zone')
    template_fields: Iterable[str] = ['project_id', 'instance_id', 'main_cluster_id', 'main_cluster_zone']
    @apply_defaults
    def __init__(self, *,