Alphanumeric Restriction

Create a function that returns True if the given string has any of the following:

• Only letters and no numbers.
• Only numbers and no letters.

If a string has both numbers and letters, or contains characters which don't fit into any category, return False

Examples

alphanumeric_restriction("Bold") ➞ True

alphanumeric_restriction("123454321") ➞ True

alphanumeric_restriction("H3LL0") ➞ False

alphanumeric_restriction("ed@bit") ➞ False

Notes

Any string that contains spaces or is empty should return False.