<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def _get_mixin_attributes(mixins):
 """Retrieve the attributes for a given set of mixin classes. The attributes of each mixin class are being merged into a single dictionary. """

    return {attribute: mixin.__dict__[attribute]
            for mixin in mixins
            for attribute in _MIXIN_ATTRIBUTES[mixin]}