import networkx as nx

DG = nx.DiGraph()

def add_claim(company, claim, evidence):

    DG.add_node(claim)
    DG.add_node(evidence)

    DG.add_edge(evidence, claim, relation="supports")


def add_contradiction(claim, evidence):

    DG.add_edge(evidence, claim, relation="contradicts")


def detect_greenwashing():

    issues = []

    for u,v,d in DG.edges(data=True):

        if d["relation"] == "contradicts":

            issues.append((u,v))

    return issues