gcs_source The Google Cloud Storage location to read the
content File content, represented as a stream of bytes. Note: As
with all ``bytes`` fields, protobuffers use a pure binary
representation, whereas JSON representations use base64.
Currently, this field only works for BatchAnnotateFiles
requests. It does not work for AsyncBatchAnnotateFiles
mime_type The type of the file. Currently only
"application/pdf", "image/tiff" and "image/gif"
are supported. Wildcards are not supported.