Parses network file and returns a network instance and a gene set.
    Attribute:
        network_fp (str): File path to a network file.

def parse_network(network_fp):
    """Parses network file and returns a network instance and a gene set.
    Attribute:
        network_fp (str): File path to a network file.
    """
    graph = nx.Graph()
    gene_set = set()

    with open(network_fp) as inFile:
        inFile.readline()  # Skip header.
        for line in inFile.readlines():
            gene1, gene2 = line.strip().split()

            graph.add_edge(gene1, gene2)
            gene_set.add(gene1)
            gene_set.add(gene2)

    return graph, gene_set