<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def check_ipv4(ip_str):
 """ Return True if is a valid IP v4 """

    try:
        socket.inet_pton(socket.AF_INET, ip_str)
    except AttributeError:
        try:
            socket.inet_aton(ip_str)
        except socket.error:
            return False
        return ip_str.count('.') == 3
    except socket.error:
        return False
    return True