class_docstr: Keeps track of `Function` protos for pprof profile.
docstr: Constructor.
  
  Args:
    string_table: A `StringTable` object.
docstr_tok: ["Constructor",".","Args",":","string_table",":","A","`","StringTable","`","object","."]
code: def __init__(self, string_table):
      """Constructor.
  
      Args:
        string_table: A `StringTable` object.
      """
      self._string_table = string_table
      # Maps tuples in the form (file_path, function_name, start_line_number)
      # to `Function` protos.
      self._function_key_to_function = {}
  
imports: from collections import defaultdict
  from collections import namedtuple
  import gzip
  import os
  import string
  import sys
  import time
  from proto import profile_pb2
label_desc: Use image node_id 1 to create a new Functions object from inherited base classes: object with example: obj = Functions(string_table)