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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 group_theta(node_length, node_idx):
 """ Returns an angle corresponding to a node of interest. Intended to be used for placing node group labels at the correct spot. :param float node_length: total number of nodes in the graph. :param int node_idx: the index of the node of interest. :returns: theta -- the angle of the node of interest in radians. """

    theta = -np.pi + node_idx * 2 * np.pi / node_length
    return theta