Blender Python script that bevels the edges of an active object that is in EDIT mode (see tutorial here: https://youtu.be/TFQMNcTj5Jw)

bmesh_bevel_from_edit_mode_mesh.py

import bpy
import bmesh

# get a reference to the active object
mesh_obj = bpy.context.active_object

# create a new bmesh and initialize it from mesh data in Edit Mode
bm = bmesh.from_edit_mesh(mesh_obj.data)

bmesh.ops.bevel(
    bm,
    geom=bm.edges,
    offset=0.2,
    segments=4,
    affect="EDGES",
    profile=0.5,
)

bm.normal_update()

# writes the bmesh data into the mesh data in Edit Mode
bmesh.update_edit_mesh(mesh_obj.data)

# clean up/free memory that was allocated for the bmesh
bm.free()