Draws iter samples from the posterior.

def sample(self, iter, length=None, verbose=0):
        """
        Draws iter samples from the posterior.
        """
        self._cur_trace_index = 0
        self.max_trace_length = iter
        self._iter = iter
        self.verbose = verbose or 0
        self.seed()

        # Assign Trace instances to tallyable objects.
        self.db.connect_model(self)

        # Initialize database -> initialize traces.
        if length is None:
            length = iter
        self.db._initialize(self._funs_to_tally, length)

        # Put traces on objects
        for v in self._variables_to_tally:
            v.trace = self.db._traces[v.__name__]

        # Loop
        self._current_iter = 0
        self._loop()
        self._finalize()