code: def visit_Import(self, node):
          
          for alias in node.names:
              current_module = MODULES
              # Recursive check for submodules
              for path in alias.name.split('.'):
                  if path not in current_module:
                      raise PythranSyntaxError(
                          "Module '{0}' unknown.".format(alias.name),
                          node)
                  else:
                      current_module = current_module[path]
docs: Check if imported module exists in MODULES.