input: Write a python function to validate if a given string is a 10-digit number using regular expressions.
  assert validate_10digit_number("1234567890") == True
  assert validate_10digit_number("12345") == False
  assert validate_10digit_number("12345678901") == False
  assert validate_10digit_number("abcdefghij") == False
output: def validate_10digit_number(s):
      import re
      return bool(re.fullmatch(r'\d{10}', s))