code: def _process_getitem(self, node, **kwargs):
          
  
          with self._interpolation():
              with self._python_bool_wrapper(**kwargs) as new_kwargs:
                  self._process_node(node.node, **new_kwargs)
  
                  if isinstance(node.arg, nodes.Slice):
                      self.output.write('.slice(')
  
                      if node.arg.step is not None:
                          raise Exception('The step argument is not supported when slicing.')
  
                      if node.arg.start is None:
                          self.output.write('0')
                      else:
                          self._process_node(node.arg.start, **new_kwargs)
  
                      if node.arg.stop is None:
                          self.output.write(')')
                      else:
                          self.output.write(',')
                          self._process_node(node.arg.stop, **new_kwargs)
                          self.output.write(')')
                  else:
                      self.output.write('[')
                      self._process_node(node.arg, **new_kwargs)
                      self.output.write(']')
docs: Processes a `GetItem` node e.g. {{ foo["bar"] }}