code: def list_operations(self, name, filter_, page_size=0, options=None):
          
          # Create the request object.
          request = operations_pb2.ListOperationsRequest(
              name=name, filter=filter_, page_size=page_size)
          return self._list_operations(request, options)
docs: Lists operations that match the specified filter in the request. If the
          server doesn't support this method, it returns ``UNIMPLEMENTED``.
          NOTE: the ``name`` binding below allows API services to override the binding
          to use different resource name schemes, such as ``users/*/operations``.
  
          Example:
            >>> from google.gapic.longrunning import operations_client
            >>> from google.gax import CallOptions, INITIAL_PAGE
            >>> api = operations_client.OperationsClient()
            >>> name = ''
            >>> filter_ = ''
            >>>
            >>> # Iterate over all results
            >>> for element in api.list_operations(name, filter_):
            >>>   # process element
            >>>   pass
            >>>
            >>> # Or iterate over results one page at a time
            >>> for page in api.list_operations(name, filter_, options=CallOptions(page_token=INITIAL_PAGE)):
            >>>   for element in page:
            >>>     # process element
            >>>     pass
  
          Args:
            name (string): The name of the operation collection.
            filter_ (string): The standard list filter.
            page_size (int): The maximum number of resources contained in the
              underlying API response. If page streaming is performed per-
              resource, this parameter does not affect the return value. If page
              streaming is performed per-page, this determines the maximum number
              of resources in a page.
            options (:class:`google.gax.CallOptions`): Overrides the default
              settings for this call, e.g, timeout, retries etc.
  
          Returns:
            A :class:`google.gax.PageIterator` instance. By default, this
            is an iterable of :class:`google.longrunning.operations_pb2.Operation` instances.
            This object can also be configured to iterate over the pages
            of the response through the `CallOptions` parameter.
  
          Raises:
            :exc:`google.gax.errors.GaxError` if the RPC is aborted.
            :exc:`ValueError` if the parameters are invalid.