input: 
  def match_numeric_strings(input_str: str) -> bool:
      """ Develop a regular expression in Python to match all numeric strings.
      >>> match_numeric_strings('123456789')
      True
      >>> match_numeric_strings('123abc456')
      False
      """
      import re
      pattern = '^[0-9]+$'
      result = re.match(pattern, input_str)
      return bool(result)
  
output:     import re
      pattern = '^[0-9]+$'
      result = re.match(pattern, input_str)
      return bool(result)