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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def node_theta(nodelist, node):
 """ Maps node to Angle. :param nodelist: Nodelist from the graph. :type nodelist: list. :param node: The node of interest. Must be in the nodelist. :returns: theta -- the angle of the node in radians. """

    assert len(nodelist) > 0, "nodelist must be a list of items."
    assert node in nodelist, "node must be inside nodelist."

    i = nodelist.index(node)
    theta = -np.pi + i * 2 * np.pi / len(nodelist)

    return theta