code: def _check_requirements(self):
          
  
          if not self._path:
              raise IOUError("IOU image is not configured")
          if not os.path.isfile(self._path) or not os.path.exists(self._path):
              if os.path.islink(self._path):
                  raise IOUError("IOU image '{}' linked to '{}' is not accessible".format(self._path, os.path.realpath(self._path)))
              else:
                  raise IOUError("IOU image '{}' is not accessible".format(self._path))
  
          try:
              with open(self._path, "rb") as f:
                  # read the first 7 bytes of the file.
                  elf_header_start = f.read(7)
          except OSError as e:
              raise IOUError("Cannot read ELF header for IOU image '{}': {}".format(self._path, e))
  
          # IOU images must start with the ELF magic number, be 32-bit or 64-bit, little endian
          # and have an ELF version of 1 normal IOS image are big endian!
          if elf_header_start != b'\x7fELF\x01\x01\x01' and elf_header_start != b'\x7fELF\x02\x01\x01':
              raise IOUError("'{}' is not a valid IOU image".format(self._path))
  
          if not os.access(self._path, os.X_OK):
              raise IOUError("IOU image '{}' is not executable".format(self._path))
docs: Checks the IOU image.