'Converts a MAC address text string to byte string.
Converts a MAC text string from a text string \'aa:aa:aa:aa:aa:aa\'
to a byte string \'xxxxxxxxxxxx\'
Args:
hwaddr: a text string containing the MAC address to convert.
Returns:
A byte string.'

@staticmethod
def mac_string_to_binary(hwaddr):

    val = ''.join([chr(b) for b in [int(c, 16) for c in hwaddr.split(':', 6)]])
    return val
