Support for root file input directly

[jiangyi15]

data format option, see full example in tf_pwa/config_loader/tests/test_root_data.yml

data:
    format: root_lhcb
    data: "data.root:tree"
    data_var: "{a}_{b}" # p4 variable, used name in  matrixto build all variable
    data_weight: "x" # formula for variable
    matrix_order: ["a", "b"] 
    matrix:
        a:  ["B", "C", "D"]
        b:  ["E", "PX", "PY", "PZ"]   
    # B_E B_PX B_PY B_PZ
    # C_E C_PX C_PY C_PZ
    # D_E D_PX D_PY D_PZ

[codecov]

Codecov Report

Merging #101 (fd994c1) into dev (8818cb7) will increase coverage by 0.23%.
The diff coverage is 91.24%.

@@            Coverage Diff             @@
##              dev     #101      +/-   ##
==========================================
+ Coverage   75.18%   75.41%   +0.23%     
==========================================
  Files         106      108       +2     
  Lines       15336    15460     +124     
  Branches     2861     2895      +34     
==========================================
+ Hits        11530    11659     +129     
+ Misses       3120     3115       -5     
  Partials      686      686              

Flag	Coverage Δ
unittests	75.41% <91.24%> (+0.23%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files Changed	Coverage Δ
tf_pwa/config_loader/config_loader.py	67.73% <ø> (+0.90%)	⬆️
tf_pwa/config_loader/plot.py	72.55% <0.00%> (-0.24%)	⬇️
tf_pwa/root_io.py	86.66% <0.00%> (-1.18%)	⬇️
tf_pwa/config_loader/data_root_lhcb.py	90.81% <90.81%> (ø)
tf_pwa/config_loader/__init__.py	100.00% <100.00%> (ø)
tf_pwa/config_loader/data.py	64.96% <100.00%> (+1.21%)	⬆️
tf_pwa/config_loader/tests/test_root_data.py	100.00% <100.00%> (ø)

... and 1 file with indirect coverage changes