class_docstr: Baseclass for linked selection functions.
  
  Subclasses override the _build_selection_streams class method to construct
  a _SelectionStreams namedtuple instance that includes the required streams
  for implementing linked selections.
  
  Subclasses also override the _expr_stream_updated method. This allows
  subclasses to control whether new selections override prior selections or
  whether they are combined with prior selections
class_docstr_tok: ["Baseclass","for","linked","selection","functions",".","Subclasses","override","the","_build_selection_streams","class","method","to","construct","a","_SelectionStreams","namedtuple","instance","that","includes","the","required","streams","for","implementing","linked","selections",".","Subclasses","also","override","the","_expr_stream_updated","method",".","This","allows","subclasses","to","control","whether","new","selections","override","prior","selections","or","whether","they","are","combined","with","prior","selections"]
docstr: Called when one of the registered HoloViews objects produces a new
  selection expression.  Subclasses should override this method, and
  they should use the input expression to update the `exprs_stream`
  property of the _SelectionStreams instance that was produced by
  the _build_selection_streams.
  
  Subclasses have the flexibility to control whether the new selection
  express overrides previous selections, or whether it is combined with
  previous selections.
code: def _expr_stream_updated(
      self, hvobj, selection_expr, bbox, region_element, **kwargs
  ):
      """
      Called when one of the registered HoloViews objects produces a new
      selection expression.  Subclasses should override this method, and
      they should use the input expression to update the `exprs_stream`
      property of the _SelectionStreams instance that was produced by
      the _build_selection_streams.
  
      Subclasses have the flexibility to control whether the new selection
      express overrides previous selections, or whether it is combined with
      previous selections.
      """
      raise NotImplementedError()
  
imports: from collections import namedtuple
  import numpy
  import param
  from param.parameterized import bothmethod
  from .core.data import Dataset
  from .core.element import Element, Layout
  from .core.layout import AdjointLayout
  from .core.options import CallbackError, Store
  from .core.overlay import NdOverlay, Overlay
  from .core.spaces import GridSpace
  from .streams import CrossFilterSet, Derived, Pipe, PlotReset, SelectionExprSequence, SelectMode, Stream
  from .util import DynamicMap
label_desc: Use image node_id 7 for calling the _base_link_selections obj's underlying member method code with example usage: obj._expr_stream_updated(hvobj, selection_expr, bbox, region_element) without return types