For LFV meson decays why quark flavors are not specified separately?

[Joro20]

For LFV B meson decays I find in the 'bpll_lfv.py' file there is no specification of different flavor of quarks! Although in the file it is mentioned that for Lepton flavour violating decays
def _define_obs_B_Mll(M, ll):
_process_tex = _hadr_lfv[M]['tex']+' '+_tex_lfv[''.join(ll)]
_process_taxonomy = r'Process :: $b$ hadron decays :: FCNC decays :: $B\to P\ell^+\ell^-$ :: $' + _process_tex + r"$"
_obs_name = "BR("+M+''.join(ll)+")"
etc.

I'm not sure how is it referring to different quark flavors for decays such as B-Ke\mu which is at quark level 'b->s' transition! Is it picking up that information from the _hadr_lfv[M] which is defined as

_hadr_lfv = { 'B0->K': {'tex': r"\bar B^0\to \bar K^0", 'B': 'B0', 'P': 'K0', }, 'B+->K': {'tex': r"B^-\to K^-", 'B': 'B+', 'P': 'K+', }, 'B0->pi': {'tex': r"\bar B^0\to \pi^0", 'B': 'B0', 'P': 'pi0', }, 'B+->pi': {'tex': r"B^-\to \pi^-", 'B': 'B+', 'P': 'pi+', }, } ?

If that is the case, then how this information is translated to the Wilson coefficients with different quark flavors ?

[DavidMStraub]

The function that does that is here
https://github.com/flav-io/flavio/blob/master/flavio/physics/bdecays/wilsoncoefficients.py#L154

[Joro20]

Thank you @DavidMStraub for pointing towards the exact location. Can you please let me know, from where is it getting the information about B and P ? Are those lists of B meson and Pseudoscalar mesons defined in
https://github.com/flav-io/flavio/blob/v2.6.1/flavio/physics/bdecays/common.py
?
But how to choose a particular set of B and P ? Also what is the role of M in the function def _define_obs_B_Mll(M, ll) ?

[DavidMStraub]

Sorry but if you want to understand exactly how the source code works, you need to look at the source code.

[Joro20]

Indeed I'm trying to understand how things works so that if I need to calculate some new observable I can have a workable code by myself! By 'source code' are you referring to understanding of Python language ? That might be problematic as I'm not familiar with the language! Instead I've invited you to look at the file (in my repository) with the particular observable that I want to calculate. If possible please let me know what I'm doing wrong. Thanks.

[DavidMStraub]

Flavio is a Python library...