<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def flatten(in_list):
 """given a list of values in_list, flatten returns the list obtained by flattening the top-level elements of in_list."""

    out_list = []
    for val in in_list:
        if isinstance(val, list):
            out_list.extend(val)
        else:
            out_list.append(val)

    return out_list