code: def expr(expression, transform=None):
      ''' Convenience function to explicitly return an "expr" specification for
      a Bokeh :class:`~bokeh.core.properties.DataSpec` property.
  
      Args:
          expression (Expression) : a computed expression for a
              ``DataSpec`` property.
  
          transform (Transform, optional) : a transform to apply (default: None)
  
      Returns:
          dict : ``{ "expr": expression }``
  
      .. note::
          This function is included for completeness. String values for
          property specifications are by default interpreted as field names.
  
      '''
      if transform:
          return dict(expr=expression, transform=transform)
      return dict(expr=expressionf expr(expression, transform=None):
      ''' Convenience function to explicitly return an "expr" specification for
      a Bokeh :class:`~bokeh.core.properties.DataSpec` property.
  
      Args:
          expression (Expression) : a computed expression for a
              ``DataSpec`` property.
  
          transform (Transform, optional) : a transform to apply (default: None)
  
      Returns:
          dict : ``{ "expr": expression }``
  
      .. note::
          This function is included for completeness. String values for
          property specifications are by default interpreted as field names.
  
      '''
      if transform:
          return dict(expr=expression, transform=transform)
      return dict(expr=expression)
docs: Convenience function to explicitly return an "expr" specification for
      a Bokeh :class:`~bokeh.core.properties.DataSpec` property.
  
      Args:
          expression (Expression) : a computed expression for a
              ``DataSpec`` property.
  
          transform (Transform, optional) : a transform to apply (default: None)
  
      Returns:
          dict : ``{ "expr": expression }``
  
      .. note::
          This function is included for completeness. String values for
          property specifications are by default interpreted as field names.