code: def _read_string(f):
      """Read a string"""
      length = _read_long(f)
      if length > 0:
          chars = _read_bytes(f, length)
          _align_32(f)
          chars = asstr(chars)
      else:
          chars = ""
      return chars
  
imports: from __future__ import division, print_function, absolute_import
  import struct
  import numpy
  from numpy.compat import asstr
  import tempfile
  import zlib
  import warnings
label_desc: Use image node_id 14 for calling a global function with example usage: _read_string(f) and returns: chars