1 | initial version |

Thanks for **Luca**'s answer! I am just expanding the code here

```
p1 = []
for m in p.iterator():
sum = 0
for x in (i_L, d, v_g, v_C):
sum += m({x:0}).is_zero()
if sum == 1:
p1.append(m)
p1
```

2 | No.2 Revision |

Thanks for **Luca**'s answer! I am just expanding the code here

```
p1 = []
for m in p.iterator():
sum = 0
for x in (i_L, d, v_g, v_C):
sum += m({x:0}).is_zero()
if sum == 1:
p1.append(m)
p1
```

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