#### Octal to Binary

V
```"""
* Author: Bama Charan Chhandogi (https://github.com/BamaCharanChhandogi)
* Description: Convert a Octal number to Binary.

References for better understanding:
https://en.wikipedia.org/wiki/Binary_number
https://en.wikipedia.org/wiki/Octal
"""

def octal_to_binary(octal_number: str) -> str:
"""
Convert an Octal number to Binary.

>>> octal_to_binary("17")
'001111'
>>> octal_to_binary("7")
'111'
>>> octal_to_binary("Av")
Traceback (most recent call last):
...
ValueError: Non-octal value was passed to the function
>>> octal_to_binary("@#")
Traceback (most recent call last):
...
ValueError: Non-octal value was passed to the function
>>> octal_to_binary("")
Traceback (most recent call last):
...
ValueError: Empty string was passed to the function
"""
if not octal_number:
raise ValueError("Empty string was passed to the function")

binary_number = ""
octal_digits = "01234567"
for digit in octal_number:
if digit not in octal_digits:
raise ValueError("Non-octal value was passed to the function")

binary_digit = ""
value = int(digit)
for _ in range(3):
binary_digit = str(value % 2) + binary_digit
value //= 2
binary_number += binary_digit

return binary_number

if __name__ == "__main__":
import doctest

doctest.testmod()
```