input: from typing import List
  
  
  def valid_numeric_strings(strings: List[str]) -> List[str]:
      """ Check if in given list of strings, each string is a valid numeric string
      (containing only digits). Return a list of valid numeric strings.
      >>> valid_numeric_strings(['123', 'abc456', '789', ''])
      ['123', '789']
      >>> valid_numeric_strings(['0', '12.34', '567', '-89'])
      ['0', '567']
      """
output:     valid_strings = []
      for s in strings:
          if s.isdigit():
              valid_strings.append(s)
      return valid_strings