input: 
  from typing import List
  
  def match_numeric_strings(strings: List[str]) -> List[str]:
      """ Match all numeric strings in the given list of strings using a regular expression.
      >>> match_numeric_strings(['123456789', 'abc123', '456def', '789'])
      ['123456789', '789']
      >>> match_numeric_strings(['hello', 'world', '123'])
      ['123']
      """
      import re
      pattern = '^[0-9]+$'
      return [s for s in strings if re.match(pattern, s)]
  
output:     import re
      pattern = '^[0-9]+$'
      return [s for s in strings if re.match(pattern, s)]