def parse_guildify_information_file(input_file, source=False):
    """
    Parses GUILDify files of information (pubmed, method_id, source (if source=True))
    """
    interaction_to_content = {}
    with open(input_file, 'r') as input_fd:
        first_line = input_fd.readline()
        for line in input_fd:
            node1, _, node2, _, content = line.strip().split()
            if source:
                content = content.split('(')[0]
            edge = frozenset([node1, node2])
            interaction_to_content.setdefault(edge, set())
            interaction_to_content[edge].add(content)
    return interaction_to_content