code: def long_substr(data):
      """Return the longest common substring in a list of strings.
  
      Credit: http://stackoverflow.com/questions/2892931/longest-common-substring-from-more-than-two-strings-python
      """
      substr = ""
      if len(data) > 1 and len(data[0]) > 0:
          for i in range(len(data[0])):
              for j in range(len(data[0]) - i + 1):
                  if j > len(substr) and all(
                      data[0][i : i + j] in x for x in data
                  ):
                      substr = data[0][i : i + j]
      elif len(data) == 1:
          substr = data[0]
      return substr
  
imports: from __future__ import absolute_import
  import os
  import re
  import sys
  import textwrap
  from string import Formatter
  from IPython.testing.skipdoctest import skip_doctest_py3, skip_doctest
  from IPython.utils import py3compat
label_desc: Use image node_id 8 for calling a global function with example usage: long_substr(data) and returns: substr