def get_text_sparsity(bbox, mentions):
b = bbox[-<NUM_LIT:4>:]<EOL>bbox_area = (b[<NUM_LIT:2>] - b[<NUM_LIT:0>]) * (b[<NUM_LIT:3>] - b[<NUM_LIT:1>])<EOL>text_area = <NUM_LIT:0><EOL>for m in mentions:<EOL><INDENT>text_area += (m.x1 - m.x0) * (m.y1 - m.y0)<EOL><DEDENT>try:<EOL><INDENT>return <NUM_LIT:1.0> * text_area / bbox_area<EOL><DEDENT>except ZeroDivisionError:<EOL><INDENT>return <NUM_LIT:0.0><EOL><DEDENT>
computes text area coverage
:param mentions:
:return: