Help in pid_task()

hey guys, i am having a small doubt in "pid_task" function in kernel/pid.c.. Assume if the type is PIDTYPE_PGID, then it means that there are multiple processes associated with the process group and each has its own task_struct..so how come the function returns the task_struct of the "head" element of the hlist_node? Sorry if my assumptions are wrong! Thanks in advance