code: def get_fake_prologue(projection_longitude, orbit_polynomials):
      """Create a fake HRIT prologue."""
      return {
          "SatelliteStatus": {
              "SatelliteDefinition": {
                  "SatelliteId": 324,
                  "NominalLongitude": -3.5,
              },
              "Orbit": {
                  "OrbitPolynomial": orbit_polynomials,
              },
          },
          "GeometricProcessing": {
              "EarthModel": {
                  "TypeOfEarthModel": 2,
                  "EquatorialRadius": 6378.169,
                  "NorthPolarRadius": 6356.5838,
                  "SouthPolarRadius": 6356.5838,
              }
          },
          "ImageDescription": {
              "ProjectionDescription": {
                  "LongitudeOfSSP": projection_longitude
              },
              "Level15ImageProduction": {"ImageProcDirection": 1},
          },
          "ImageAcquisition": {
              "PlannedAcquisitionTime": {
                  "TrueRepeatCycleStart": datetime(
                      2006, 1, 1, 12, 15, 9, 304888
                  ),
                  "PlannedRepeatCycleEnd": datetime(
                      2006, 1, 1, 12, 30, 0, 0
                  ),
              }
          },
      }
  
file_path: satpy/satpy/tests/reader_tests/test_seviri_l1b_hrit_setup.py
imports: from datetime import datetime
  from unittest import mock
  import numpy
  from satpy.readers.seviri_l1b_hrit import HRITMSGFileHandler, HRITMSGPrologueFileHandler
  from satpy.tests.reader_tests.test_seviri_base import ORBIT_POLYNOMIALS
label_desc: Use image node_id 4 for calling a global function with example usage: get_fake_prologue(projection_longitude, orbit_polynomials) and returns: dict