gettp() does not separate the IF's in a nodding example

[teuben]

Describe the bug gettp() returns a single scanblock, even if no ifnum= is specified when there are multple IF's.

How to Reproduce

# from acceptance_testing/data/
sdf=GBTFITSLoad('TSCAL_19Nov2015/TSCAL_19Nov2015.raw.acs/TSCAL_19Nov2015.raw.acs.fits')

sdf.gettp(scan=6,fdnum=0,plnum=0)
sdf.gettp(scan=6,fdnum=0,plnum=0,ifnum=0)
sdf.gettp(scan=6,fdnum=0,plnum=0,ifnum=1)

each returns a single scanblock, but the first one should return 2.

It seems, only the first is returned in this case:

print(sdf.gettp(scan=6,fdnum=0,plnum=0)[0].timeaverage().stats())
print(sdf.gettp(scan=6,fdnum=0,plnum=0,ifnum=0)[0].timeaverage().stats())
print(sdf.gettp(scan=6,fdnum=0,plnum=0,ifnum=1)[0].timeaverage().stats())

(<Quantity 3.10215706 ct>, 1.3773813265212864, <Quantity 0.03795753 ct>, <Quantity 5.53300124 ct>)
(<Quantity 3.10215706 ct>, 1.3773813265212864, <Quantity 0.03795753 ct>, <Quantity 5.53300124 ct>)
(<Quantity 2.67228504 ct>, 1.078213412987175, <Quantity 0.0481095 ct>, <Quantity 12.03663866 ct>)

Environment

• Dysh version 0.3
• Python version 3.11.7
• OS linux/ubuntu 22.04

[teuben]

And to come back to an earlier point, the following example shows POL is special.

sdf.gettp(scan=6,fdnum=1,plnum=1,ifnum=1)[0].fdnum    #ok
sdf.gettp(scan=6,fdnum=1,plnum=1,ifnum=1)[0].plnum    #  fails
sdf.gettp(scan=6,fdnum=1,plnum=1,ifnum=1)[0].ifnum    #ok

[mpound]

ScanBlocks can have different IFs, Scans cannot. This is not technically a bug. But we have to decide if we want to change the behavior of ScanBlock

[mpound]

See also #332