input: Write a python function to convert a string of hexadecimal values separated by spaces into its decimal equivalent.
  assert convert_hexvals_to_decimal("7a 0d 72") == 8032818
  assert convert_hexvals_to_decimal("00 01 00") == 65536
  assert convert_hexvals_to_decimal("ff ff") == 65535
output: def convert_hexvals_to_decimal(hex_string):
      hex_vals = hex_string.split()
      decimal_value = 0
      for hex_val in hex_vals:
          decimal_value = (decimal_value << 8) + int(hex_val, 16)
      return decimal_value