code: def long_substring(str_a, str_b):
      
      data = [str_a, str_b]
      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]
      return substr.strip()
docs: Looks for a longest common string between any two given strings passed
      :param str_a: str
      :param str_b: str
  
      Big Thanks to Pulkit Kathuria(@kevincobain2000) for the function
      The function is derived from jProcessing toolkit suite