@staticmethod
def _interpret_input_from_face_vertices(faces, purge):
    """Get faces and vertices from a list of faces as points."""
    vertices = []
    face_collector = []
    if purge:
        for f in faces:
            ind = []
            for v in f:
                try:
                    ind.append(vertices.index(v))
                except ValueError:
                    vertices.append(v)
                    ind.append(len(vertices) - 1)
            face_collector.append(tuple(ind))
    else:
        ver_counter = 0
        for f in faces:
            ind = []
            for v in f:
                vertices.append(v)
                ind.append(ver_counter)
                ver_counter += 1
            face_collector.append(tuple(ind))
    return vertices, face_collector
