When you say that you are a lawyer, an electrician, an engineer etc. by training, this means that you received a formal education ( or training ) in your particular area of expertise. In other words, saying that you are somebody by training puts emphasis the fact that you are legally qualified to do your job
دانش آموخته ی ( مهندسی، حقوق، وکالت، برق. . . )
دانش آموخته ی ( مهندسی، حقوق، وکالت، برق. . . )