'Create new depend instance.
@param os: OS name. must be non-empty
@type  os: str
@param version: OS version. must be non-empty
@type  version: str
@param notes: (optional) notes about platform support
@type  notes: str'

def __init__(self, os, version, notes=None):

    if (not os):
        raise ValueError("bad    'os'    attribute")
    if (not version):
        raise ValueError("bad    'version'    attribute")
    self.os = os
    self.version = version
    self.notes = notes
