Maya attributes can have categories assigned to them. We can implement our own categories in attributes at creation time. This function returns a list of categories present in a Maya object's attributes.

getAttrCategories_20161024.py

from pymel.core import
def getAttrCategories(obj=None):
    '''
    Maya attributes can have categories assigned to them
    we can implement our own categories in attributes at creation time
    this function returns a list of categories present in a Maya object's attributes
    '''
    if not obj:
        print 'getAttrCategories: no objects passed in. aborted'
        return
    categories=[]
    for x in PyNode('shaderPublish_infoNode').listAttr():
        # print x
        try:
            # attributeQuery will return a list
            attrCat = attributeQuery(x.longName(), node='shaderPublish_infoNode', categories=True)
            for item in attrCat:
                if not item in categories:
                    categories.append(item)
        except:
            pass
    return categories
getAttrCategories(ls(sl=True)[0])