code: def where(boolean_expr, true_expr, false_null_expr):
      
      op = ops.Where(boolean_expr, true_expr, false_null_expr)
      return op.to_expr()
docs: Equivalent to the ternary expression: if X then Y else Z
  
      Parameters
      ----------
      boolean_expr : BooleanValue (array or scalar)
      true_expr : value
        Values for each True value
      false_null_expr : value
        Values for False or NULL values
  
      Returns
      -------
      result : arity depending on inputs
        Type of true_expr used to determine output type