code: def write_cachegrind(self, f):
      if isinstance(f, str):
          f = open(f, "w")
          f.write("events: Microseconds\n")
          f.write("fl=sympyallimport\n")
          must_close = True
      else:
          must_close = False
  
      f.write("fn=%s\n" % self.name())
      f.write("1 %s\n" % self.exclusive_time())
  
      counter = 2
      for child in self.children():
          f.write("cfn=%s\n" % child.name())
          f.write("calls=1 1\n")
          f.write("%s %s\n" % (counter, child.time()))
          counter += 1
  
      f.write("\n\n")
  
      for child in self.children():
          child.write_cachegrind(f)
  
      if must_close:
          f.close()
  
imports: from __future__ import print_function
  import timeit
  from sympy import *
label_desc: Use image node_id 15 for calling the TreeNode obj's underlying member method code with example usage: obj.write_cachegrind(f) without return types