def list_documents(self,<EOL>parent,<EOL>page_size=None,<EOL>retry=google.api_core.gapic_v1.method.DEFAULT,<EOL>timeout=google.api_core.gapic_v1.method.DEFAULT,<EOL>metadata=None):
<EOL>if '<STR_LIT>' not in self._inner_api_calls:<EOL><INDENT>self._inner_api_calls[<EOL>'<STR_LIT>'] = google.api_core.gapic_v1.method.wrap_method(<EOL>self.transport.list_documents,<EOL>default_retry=self._method_configs['<STR_LIT>'].retry,<EOL>default_timeout=self._method_configs['<STR_LIT>']<EOL>.timeout,<EOL>client_info=self._client_info,<EOL>)<EOL><DEDENT>request = document_pb2.ListDocumentsRequest(<EOL>parent=parent,<EOL>page_size=page_size,<EOL>)<EOL>iterator = google.api_core.page_iterator.GRPCIterator(<EOL>client=None,<EOL>method=functools.partial(<EOL>self._inner_api_calls['<STR_LIT>'],<EOL>retry=retry,<EOL>timeout=timeout,<EOL>metadata=metadata),<EOL>request=request,<EOL>items_field='<STR_LIT>',<EOL>request_token_field='<STR_LIT>',<EOL>response_token_field='<STR_LIT>',<EOL>)<EOL>return iterator<EOL>
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.