§ 501. Representation. Any person compelled to appear in person or who voluntarily appears before any agency or representative thereof shall be accorded the right to be accompanied, represented and advised by counsel. In a proceeding before an agency, every party or person shall be accorded the right to appear in person or by or with counsel. Nothing herein shall be construed either to grant or to deny to any person who is not a lawyer the right to appear for or represent others before any agency.