'Selects nodes that match a label and course_key
Args:
label: the string of the label we\'re selecting nodes by
course_key: the string of the course key we\'re selecting node by
Returns: a MockResult of matching nodes'

def select(self, label, course_key):

    nodes = []
    for node in self.graph.nodes:
        if (node.has_label(label) and (node[u'course_key'] == course_key)):
            nodes.append(node)
    return MockNodeSelection(nodes)
