<｜begin▁of▁sentence｜>### Instruction:
Assuming there's a need to validate that a given numerical input parameter represents a positive value before proceeding with further calculations in a mathematical application. How would the 'check_argument' function be used to enforce this condition, and what happens if the input is not a positive number?
### Response:
import graspologic

# Function to check if the input number is positive
def is_positive(number):
    check = number > 0
    message = 'Number must be positive.'
    graspologic.preconditions.check_argument(check, message)

# Example usage: Checking if the input number is positive
try:
    is_positive(-5)
except ValueError as e:
    print(e)
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