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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 add_edges(self, from_idx, to_idx, weight=1, symmetric=False, copy=False):
    '''Adds all from->to edges. weight may be a scalar or 1d array.
    If symmetric=True, also adds to->from edges with the same weights.'''
    raise NotImplementedError()