Write a Python function `count_digits` that takes a single string as input and returns the number of digit characters (`0-9`) present in the string.
#### Example Usage
```python [main.nopy]
print(count_digits("hello123")) # Output: 3
print(count_digits("abc")) # Output: 0
print(count_digits("2023!")) # Output: 4
```def count_digits(input_string):
"""
Count the number of digit characters in the given string.
Args:
input_string (str): The string to analyze.
Returns:
int: The count of digit characters in the string.
"""
# Initialize a counter for digits
digit_count = 0
# TODO: Loop over the characters and count the ones that are digits
return digit_count