input: 
  import re 
  
  def match_numeric_strings(strings: str) -> bool:
      """
      Develop a regular expression in Python to match all numeric strings.
      
      >>> match_numeric_strings('123456789')
      True
      >>> match_numeric_strings('abc123')
      False
      >>> match_numeric_strings('123.456')
      False
      >>> match_numeric_strings('0')
      True
      """
      pattern = '^[0-9]+$'
      result = re.match(pattern, strings) 
      return bool(result)
  
output:     pattern = '^[0-9]+$'
      result = re.match(pattern, strings) 
      return bool(result)