Add guppy backend

[dxe4]

related to my comment here #236 (comment)
with implementation of guppy3 we can get the right values.

note this implementation does self.prevlines[-1] == self.prev_lineno: for guppy backend only, because repeating [i for i in range(0, 10000000)] makes the guppy backend extremely slow. although this may not be ideal or acceptable i thought it's worth sharing the code.

@profile
def myfn_py():
ones = [1] * NBR_ITEMS
twos = [i + 1 for i in ones]
return twos
@profile
def myfn_np():
ones_np = np.ones(NBR_ITEMS)
twos_np = ones_np+1
return twos_np
myfn_np()
myfn_py()
python -m memory_profiler --backend guppy prof.py Line # Mem usage Increment Line Contents
================================================
11 14.191 MiB 14.191 MiB @profile
12 def myfn_py():
13 18.006 MiB 3.815 MiB ones = [1] * NBR_ITEMS
14 22.098 MiB 4.091 MiB twos = [i + 1 for i in ones]
15 return twos
Filename: prof.py
Line # Mem usage Increment Line Contents
================================================
18 14.189 MiB 14.189 MiB @profile
19 def myfn_np():
20 18.005 MiB 3.817 MiB ones_np = np.ones(NBR_ITEMS)
21 21.820 MiB 3.815 MiB twos_np = ones_np+1
22 21.820 MiB 0.000 MiB return twos_np

[dxe4]

this can cause issues if you want to measure the memory of a side effect eg

[foo() for i in range(0, 500)]
def foo():
make_big_array = [i for i in random.randint(0, int(1e9))]

i haven't tested it.
although it will give correct results for this case #236 (comment)