code: def l2_af_schema(settings=None):
      """Define schema for LI L2 AF product."""
      settings = settings or {}
      nobs = settings.get("num_obs", 1234)
  
      return {
          "providers": settings.get("providers", {}),
          "variable_path": settings.get("variable_path", ""),
          "dimensions": accumulation_dimensions(1, nobs),
          "variables": {
              "accumulation_offsets": {
                  "format": "u4",
                  "shape": ("accumulations",),
                  "default_data": lambda: 0,
              },
              "accumulation_start_times": {
                  "format": "f8",
                  "shape": ("accumulations",),
                  "default_data": lambda: 4.25055600161e8,
              },
              "l1b_geolocation_warning": {
                  "format": "i1",
                  "shape": ("accumulations",),
                  "long_name": "L1b geolocation warning",
                  "default_data": lambda: -127,
              },
              "l1b_radiometric_warning": {
                  "format": "i1",
                  "shape": ("accumulations",),
                  "long_name": "L1b radiometric warning",
                  "default_data": lambda: -127,
              },
              "average_flash_qa": {
                  "format": "i1",
                  "shape": ("accumulations",),
                  "default_data": lambda: 23,
              },
              "flash_accumulation": {
                  "format": "u2",
                  "shape": ("pixels",),
                  "default_data": lambda: np.clip(
                      np.round(np.random.normal(1, 2, nobs)),
                      1,
                      2**16 - 1,
                  ),
              },
              "mtg_geos_projection": mtg_geos_projection(),
              "x": fci_grid_definition("X", nobs),
              "y": fci_grid_definition("Y", nobs),
          },
      }
  
imports: from datetime import datetime
  import numpy
  import xarray
  from satpy.tests.reader_tests.test_netcdf_utils import FakeNetCDF4FileHandler
label_desc: Use image node_id 5 for calling a global function with example usage: l2_af_schema(settings) and returns: dict