<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def is_subdir(child, parent):
 """ Determine if "child" is a subdirectory of "parent". If child == parent, returns True. """

    child_path = os.path.realpath(child)
    parent_path = os.path.realpath(parent)

    if len(child_path) < len(parent_path):
        return False

    for i in range(len(parent_path)):
        if parent_path[i] != child_path[i]:
            return False

    return True