Wrong default duration in make_trapezoid

[schuenke]

Describe the bug
With b5bd54a the default duration of make_trapezoid() was changed from 0 to 4e-3. However, the make_trapezoid() function is often used to create a rephasing gradient (usually named gzr) with minimum duration. This does not work anymore, because it's always using the default duration of 4e-3 now leading to much larger minimum echo times etc

To Reproduce

• create an rf pulse (e.g. using pp.make_sinc_pulse()) and set return_gz = True
• check the duration of the rephasing gradient (gzr) using pp.calc_duration()

Expected behavior
Calling make_trapezoid() without specifying a duration should create a gradient with minium possible duration

Solution to fix the problem
Change the default duration back to 0.

[schuenke]

I think the default duration of 4e-3 for the rf pulses was fine, but for the trapezoid gradients it didn't make any sense!? You changed it for the pulses now, but not for the mentioned gradient.

[sravan953]

Oops looks like I reverted the wrong commit - need to learn to make more accurate commits! This is the commit I actually need to fix - b5bd54a. Will try to figure out how to squash the previous and the next commits so I can try to keep the tree clean.

[sravan953]

Hopefully the latest commit fixes things!