Write a python function char$\_$ind which accepts two parameters, a string and a character $($char$),$ which in Python will also have the datatype $$string$.$ The function should return a list with the indices at which the character appears in the string. If the character does not appear in the string, the function should return an empty list.

$$ Function Name: char$\_$ind

$$ Parameters: string, string

$$ Return Value: list

Example: if I pass the parameters 'Hello World!$\text{'}$ and $\text{'}$l$\text{'},$ the return value should be $[2,3,9].$ However, if I pass the parameters 'Welcome' and $\text{'}$a$\text{'},$ the return value should be $[]$