code: def cluster(
          self, cluster_id, location_id=None, serve_nodes=None, default_storage_type=None
      ):
          
          return Cluster(
              cluster_id,
              self,
              location_id=location_id,
              serve_nodes=serve_nodes,
              default_storage_type=default_storage_type,
          )
docs: Factory to create a cluster associated with this instance.
  
          For example:
  
          .. literalinclude:: snippets.py
              :start-after: [START bigtable_create_cluster]
              :end-before: [END bigtable_create_cluster]
  
          :type cluster_id: str
          :param cluster_id: The ID of the cluster.
  
          :type instance: :class:`~google.cloud.bigtable.instance.Instance`
          :param instance: The instance where the cluster resides.
  
          :type location_id: str
          :param location_id: (Creation Only) The location where this cluster's
                              nodes and storage reside. For best performance,
                              clients should be located as close as possible to
                              this cluster.
                              For list of supported locations refer to
                              https://cloud.google.com/bigtable/docs/locations
  
          :type serve_nodes: int
          :param serve_nodes: (Optional) The number of nodes in the cluster.
  
          :type default_storage_type: int
          :param default_storage_type: (Optional) The type of storage
                                       Possible values are represented by the
                                       following constants:
                                       :data:`google.cloud.bigtable.enums.StorageType.SSD`.
                                       :data:`google.cloud.bigtable.enums.StorageType.SHD`,
                                       Defaults to
                                       :data:`google.cloud.bigtable.enums.StorageType.UNSPECIFIED`.
  
          :rtype: :class:`~google.cloud.bigtable.instance.Cluster`
          :returns: a cluster owned by this instance.