'Filters info, looking for keys, optionally set with a given value
:type info: list of lines
:param info: result of utility method get_info()
:type key: string
:param key: filter based on this key
:type value: string
:param value: filter based on this value
:return: value or None'

def _info_filter(self, info, key, value=None):

    for line in info:
        if (value is not None):
            looking_for = ('%s=%s' % (key, value))
            if (line == looking_for):
                return line.split('=')[1]
        elif line.startswith(('%s=' % key)):
            return line.split('=')[1]
    return None
