<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def area(poly):
 """Calculation of zone area"""

    poly_xy = []
    num = len(poly)
    for i in range(num):
        poly[i] = poly[i][0:2] + (0,)
        poly_xy.append(poly[i])
    return surface.area(poly)