input: def match_numeric_strings(input_string: str) -> bool:
      """Match all numeric strings using a regular expression in Python.
      >>> match_numeric_strings('123456789')
      True
      >>> match_numeric_strings('abc123456789')
      False
      >>> match_numeric_strings('')
      False
      """
  
output:     import re
      pattern = r'^\d+$'
      return bool(re.match(pattern, input_string))