[BUG] Error reading SigMf formatted file

[drabastomek]

Describe the bug
Error reading SigMf formatted file from a folder located .. from where the code is executed. This is due to the way the .sigmf-meta file is constructed if meta_file parameter is not specified.

Steps/Code to reproduce bug
Minimal example

data = cusignal.read_sigmf(
    data_file='../data/Demod_WiFi_cable_X310_3123D76_IQ#1_run1.sigmf-data'
)

Full stack:

---------------------------------------------------------------------------
FileNotFoundError                         Traceback (most recent call last)
<ipython-input-46-cda23b1650a7> in <module>
      1 data = cusignal.read_sigmf(
----> 2     data_file='../data/Demod_WiFi_cable_X310_3123D76_IQ#1_run1.sigmf-data'
      3 )
      4 data

/opt/conda/envs/rapids/lib/python3.7/site-packages/cusignal/io/reader.py in read_sigmf(data_file, meta_file, buffer, num_samples, offset)
    160         meta_file = split_string[0] + meta_ext
    161 
--> 162     with open(meta_file, "r") as f:
    163         header = json.loads(f.read())
    164 

FileNotFoundError: [Errno 2] No such file or directory: '.sigmf-meta'

Expected behavior
SigMf formatted signal data is read properly.

Environment details (please complete the following information):

• Environment location: Docker
• Method of cuSignal install: Docker
  • Stable git pull from rapidsai/rapidsai, v 0.16, CUDA 11, Python 3.7.8