bmesh.py

import bpy

def ensure_custom_data_layers(bm, vertex_groups=True, bevel_weights=True, crease=True):

    vert_vg_layer = bm.verts.layers.deform.verify() if vertex_groups else None
    if bpy.app.version >= (4, 0, 0):

        if bevel_weights:
            edge_bw_layer = bm.edges.layers.float.get('bevel_weight_edge')

            if not edge_bw_layer:
                edge_bw_layer = bm.edges.layers.float.new('bevel_weight_edge')
        else:
            edge_bw_layer = None

        if crease:
            edge_crease_layer = bm.edges.layers.float.get('crease_edge')

            if not edge_crease_layer:
                edge_crease_layer = bm.edges.layers.float.new('crease_edge')
        else:
            edge_crease_layer = None
    else:
        edge_bw_layer = bm.edges.layers.bevel_weight.verify() if bevel_weights else None
        edge_crease_layer = bm.edges.layers.crease.verify() if crease else None

    return [layer for layer in [vert_vg_layer, edge_bw_layer, edge_crease_layer] if layer is not None]

def get_loop_triangles(bm, faces=None):
    if faces:
        return [lt for lt in bm.calc_loop_triangles() if lt[0].face in faces]
    return bm.calc_loop_triangles()

def get_tri_coords_from_face(loop_triangles, f, mx=None):
    if mx:
        return [mx @ l.vert.co for lt in loop_triangles if lt[0].face == f for l in lt]
    else:
        return [l.vert.co for lt in loop_triangles if lt[0].face == f for l in lt]