Parameters
		----------
		target_term_doc_mat : TermDocMatrix

		Returns
		-------
		PriorFactory

def align_to_target(self, target_term_doc_mat):
		'''
		Parameters
		----------
		target_term_doc_mat : TermDocMatrix

		Returns
		-------
		PriorFactory
		'''
		self.priors = self.priors[target_term_doc_mat.get_terms()].fillna(0)
		return self