def _clone_vertex_with_new_tangents(self, prim_index, vertex_index, tangent, binormal):
        clone_index = len(self.positions)
        self.positions.append(self.positions[vertex_index])
        self.normals.append(self.normals[vertex_index])
        for uvs in self.uvs:
            if len(uvs) > vertex_index:
                uvs.append(uvs[vertex_index])
        self.tangents.append(tangent)
        self.binormals.append(binormal)
        if len(self.colors) > vertex_index:
            self.colors.append(self.colors[vertex_index])
        if len(self.skin_indices) > vertex_index:
            self.skin_indices.append(self.skin_indices[vertex_index])
        if len(self.skin_weights) > vertex_index:
            self.skin_weights.append(self.skin_weights[vertex_index])
        return clone_index
Create a new vertex clone all attributes. Then set the new tangent and binormal.
dataset/ETHPy150Open turbulenz/turbulenz_tools/turbulenz_tools/tools/mesh.py/Mesh._clone_vertex_with_new_tangents