code: def check_point(coord):
      if not isinstance(coord, list):
          return "each position must be a list"
      if len(coord) not in (2, 3):
          return "a position must have exactly 2 or 3 values"
      for number in coord:
          if not isinstance(number, Number):
              return "a position cannot have inner positions"
  
imports: from decimal import Decimal
  from numbers import Number, Real
  from geojson.base import GeoJSON
label_desc: Use image node_id 1 for calling a global function with example usage: check_point(coord) and returns: str, str, str