input: def match_numeric_strings(string: str) -> bool:
      """ Match a given string to check if it contains only numeric characters.
      >>> match_numeric_strings('123456789')
      True
      >>> match_numeric_strings('123abc456')
      False
      """
      import re
      pattern = '^[0-9]+$'
      result = re.match(pattern, string)
      return bool(result)
output:     import re
      pattern = '^[0-9]+$'
      result = re.match(pattern, string)
      return bool(result)