'Retrieve a document by document ID.
Args:
doc_id: The ID of the document to retreive.
Kwargs:
deadline: Deadline for RPC call in seconds; if None use the default.
Returns:
If the document ID exists, returns the associated document. Otherwise,
returns None.
Raises:
TypeError: If any of the parameters have invalid types, or an unknown
attribute is passed.
ValueError: If any of the parameters have invalid values (e.g., a
negative deadline).'

@datastore_rpc._positional(2)
def get(self, doc_id, deadline=None):

    return self.get_async(doc_id, deadline=deadline).get_result()
