<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def create(self, reference, document_data):
 """Add a "change" to this batch to create a document. If the document given by ``reference`` already exists, then this batch will fail when :meth:`commit`-ed. Args: reference (~.firestore_v1beta1.document.DocumentReference):
 A document reference to be created in this batch. document_data (dict):
 Property names and values to use for creating a document. """

        write_pbs = _helpers.pbs_for_create(reference._document_path, document_data)
        self._add_write_pbs(write_pbs)