code: def read_digits(self, start: int, char: str) -> int:
          
          source = self.source
          body = source.body
          position = start
          while "0" <= char <= "9":
              position += 1
              char = body[position : position + 1]
          if position == start:
              raise GraphQLSyntaxError(
                  source,
                  position,
                  f"Invalid number, expected digit but got: {print_char(char)}.",
              )
          return position
docs: Return the new position in the source after reading digits.