class_docstr: Abstract base class for Row and Column. Do not use directly.
  
      
class_docstr_tok: ["Abstract","base","class","for","Row","and","Column",".","Do","not","use","directly","."]
code: def _check_child_is_also_root(self):
      problems = []
      for c in self.children:
          if c.document is not None and c in c.document.roots:
              problems.append(str(c))
      if problems:
          return ", ".join(problems)
      else:
          return None
  
imports: from __future__ import annotations
  import logging
  from ..colors import RGB, Color, ColorLike
  from ..core.enums import Align, Dimensions, FlowMode, Location, ScrollbarPolicy, SizingMode, SizingPolicy
  from ..core.has_props import HasProps, abstract
  from ..core.properties import Auto, Bool, Either, Enum, Float, Instance, Int, List, NonNegative, Null, Nullable, String, Struct, Tuple
  from ..core.property.struct import Optional
  from ..core.property_aliases import GridSpacing, Pixels, TracksSizing
  from ..core.validation import error, warning
  from ..core.validation.errors import MIN_PREFERRED_MAX_HEIGHT, MIN_PREFERRED_MAX_WIDTH, REPEATED_LAYOUT_CHILD
  from ..core.validation.warnings import BOTH_CHILD_AND_ROOT, EMPTY_LAYOUT, FIXED_HEIGHT_POLICY, FIXED_SIZING_MODE, FIXED_WIDTH_POLICY
  from ..model import Model
  from .ui.menus import Menu
  from .ui.tooltips import Tooltip
  from .ui.ui_element import UIElement
label_desc: Use image node_id 3 for calling the FlexBox obj's underlying member method code with example usage: obj._check_child_is_also_root() and returns: str, None