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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 cm_json_to_graph(im_json):
 """Return pygraphviz Agraph from Kappy's contact map JSON. Parameters im_json : dict A JSON dict which contains a contact map generated by Kappy. Returns ------- graph : pygraphviz.Agraph A graph representing the contact map. """

    cmap_data = im_json['contact map']['map']

    # Initialize the graph
    graph = AGraph()

    # In this loop we add sites as nodes and clusters around sites to the
    # graph. We also collect edges to be added between sites later.
    edges = []
    for node_idx, node in enumerate(cmap_data):
        sites_in_node = []
        for site_idx, site in enumerate(node['node_sites']):
            # We map the unique ID of the site to its name
            site_key = (node_idx, site_idx)
            sites_in_node.append(site_key)
            graph.add_node(site_key, label=site['site_name'], style='filled',
                           shape='ellipse')
            # Each port link is an edge from the current site to the
            # specified site
            if not site['site_type'] or not site['site_type'][0] == 'port':
                continue
            for port_link in site['site_type'][1]['port_links']:
                edge = (site_key, tuple(port_link))
                edges.append(edge)
        graph.add_subgraph(sites_in_node,
                           name='cluster_%s' % node['node_type'],
                           label=node['node_type'])

    # Finally we add the edges between the sites
    for source, target in edges:
        graph.add_edge(source, target)

    return graph