Returns the list of all documents of the knowledge base.

        Example:
            >>> import dialogflow_v2beta1
            >>>
            >>> client = dialogflow_v2beta1.DocumentsClient()
            >>>
            >>> parent = client.knowledge_base_path('[PROJECT]', '[KNOWLEDGE_BASE]')
            >>>
            >>> # Iterate over all results
            >>> for element in client.list_documents(parent):
            ...     # process element
            ...     pass
            >>>
            >>>
            >>> # Alternatively:
            >>>
            >>> # Iterate over results one page at a time
            >>> for page in client.list_documents(parent, options=CallOptions(page_token=INITIAL_PAGE)):
            ...     for element in page:
            ...         # process element
            ...         pass

        Args:
            parent (str): Required. The knowledge base to list all documents for.
                Format: ``projects/<Project ID>/knowledgeBases/<Knowledge Base ID>``.
            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.
            retry (Optional[google.api_core.retry.Retry]):  A retry object used
                to retry requests. If ``None`` is specified, requests will not
                be retried.
            timeout (Optional[float]): The amount of time, in seconds, to wait
                for the request to complete. Note that if ``retry`` is
                specified, the timeout applies to each individual attempt.
            metadata (Optional[Sequence[Tuple[str, str]]]): Additional metadata
                that is provided to the method.

        Returns:
            A :class:`~google.gax.PageIterator` instance. By default, this
            is an iterable of :class:`~google.cloud.dialogflow_v2beta1.types.Document` instances.
            This object can also be configured to iterate over the pages
            of the response through the `options` parameter.

        Raises:
            google.api_core.exceptions.GoogleAPICallError: If the request
                    failed for any reason.
            google.api_core.exceptions.RetryError: If the request failed due
                    to a retryable error and retry attempts failed.
            ValueError: If the parameters are invalid.

def list_documents(self,
                       parent,
                       page_size=None,
                       retry=google.api_core.gapic_v1.method.DEFAULT,
                       timeout=google.api_core.gapic_v1.method.DEFAULT,
                       metadata=None):
        """
        Returns the list of all documents of the knowledge base.

        Example:
            >>> import dialogflow_v2beta1
            >>>
            >>> client = dialogflow_v2beta1.DocumentsClient()
            >>>
            >>> parent = client.knowledge_base_path('[PROJECT]', '[KNOWLEDGE_BASE]')
            >>>
            >>> # Iterate over all results
            >>> for element in client.list_documents(parent):
            ...     # process element
            ...     pass
            >>>
            >>>
            >>> # Alternatively:
            >>>
            >>> # Iterate over results one page at a time
            >>> for page in client.list_documents(parent, options=CallOptions(page_token=INITIAL_PAGE)):
            ...     for element in page:
            ...         # process element
            ...         pass

        Args:
            parent (str): Required. The knowledge base to list all documents for.
                Format: ``projects/<Project ID>/knowledgeBases/<Knowledge Base ID>``.
            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.
            retry (Optional[google.api_core.retry.Retry]):  A retry object used
                to retry requests. If ``None`` is specified, requests will not
                be retried.
            timeout (Optional[float]): The amount of time, in seconds, to wait
                for the request to complete. Note that if ``retry`` is
                specified, the timeout applies to each individual attempt.
            metadata (Optional[Sequence[Tuple[str, str]]]): Additional metadata
                that is provided to the method.

        Returns:
            A :class:`~google.gax.PageIterator` instance. By default, this
            is an iterable of :class:`~google.cloud.dialogflow_v2beta1.types.Document` instances.
            This object can also be configured to iterate over the pages
            of the response through the `options` parameter.

        Raises:
            google.api_core.exceptions.GoogleAPICallError: If the request
                    failed for any reason.
            google.api_core.exceptions.RetryError: If the request failed due
                    to a retryable error and retry attempts failed.
            ValueError: If the parameters are invalid.
        """
        # Wrap the transport method to add retry and timeout logic.
        if 'list_documents' not in self._inner_api_calls:
            self._inner_api_calls[
                'list_documents'] = google.api_core.gapic_v1.method.wrap_method(
                    self.transport.list_documents,
                    default_retry=self._method_configs['ListDocuments'].retry,
                    default_timeout=self._method_configs['ListDocuments']
                    .timeout,
                    client_info=self._client_info,
                )

        request = document_pb2.ListDocumentsRequest(
            parent=parent,
            page_size=page_size,
        )
        iterator = google.api_core.page_iterator.GRPCIterator(
            client=None,
            method=functools.partial(
                self._inner_api_calls['list_documents'],
                retry=retry,
                timeout=timeout,
                metadata=metadata),
            request=request,
            items_field='documents',
            request_token_field='page_token',
            response_token_field='next_page_token',
        )
        return iterator