# Lenguaje net::=     <block_vertices>
#                     <block_arcs>
#  		      <block_edges>
# <block_vertices>::=  "*Vertices"
#                       <num_vertices>
#                       <list_vertices>
# <block_arcs>::=     "*Arcs"
#                     <list_arcs> 
# <block_edges>::=    "*Edges"
#                     <List_edges>
#
# <list_vertices>::=  <nun_vertices>
#                     <name_vertice>
# <list_options>::=   | <option_shape>
#                     | <opction_colour>
#                     | <option_time>
# <List_arcs>::=    <nun_vertice_origin>
#                   <nun_vertice_dest>
#                    "1"
# <List_edges>::=    <draw_option>