docstr: Return precision for a given recall
code: def precision_at_recall(self, recall, label=None):
      """Return precision for a given recall"""
      if label:
          label_id = self.f.get_label_id(label)
          precision = self.m.precisionAtRecallLabel(label_id, recall)
      else:
          precision = self.m.precisionAtRecall(recall)
  
      return precision
  
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  from __future__ import unicode_literals
  import fasttext_pybind
  import numpy
  import multiprocessing
  import sys
  from itertools import chain
label_desc: Use image node_id 4 for calling the _Meter obj's underlying member method code with example usage: obj.precision_at_recall(recall, label) and returns: precision