input: def check_bracket_nesting(string):
      '''
      Define a function that examines a string composed solely of square brackets.
      The function should return True if the brackets contain at least one nested subsequence.
  
      check_bracket_nesting('[[]]') ➞ True
      check_bracket_nesting('[]]]]]]][[[[[]') ➞ False
      check_bracket_nesting('[][]') ➞ False
      check_bracket_nesting('[]') ➞ False
      check_bracket_nesting('[[][]]') ➞ True
      check_bracket_nesting('[[]][[') ➞ True
      '''
output:     stack = []
      nested_found = False
      for char in string:
          if char == '[':
              stack.append('[')
              if len(stack) > 1:
                  nested_found = True
          elif char == ']' and stack:
              stack.pop()
      return nested_found and not stack