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Given the following text description, write Python code to implement the functionality described below step by step
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Description:
 "Third" Light
Setup
Let's first make sure we have the latest version of PHOEBE 2.0 installed. (You can comment out this line if you don't use pip for your installation or don't want to update to the latest release).
Step1:  As always, let's do imports and initialize a logger and a new bundle.  See Building a System for more details.
Step2:  Relevant Parameters
The 'l3' parameter describes how much third light exists in a given passband.  Since this is passband dependent and only used for flux measurments - it does not yet exist for a new empty Bundle.
Step3:  So let's add a LC dataset
Step4:  We now see that the LC dataset created an 'l3' parameters for the new dataset.
Step5:  Influence on Light Curves (Fluxes)
"Third" light is simply additional flux added to the light curve from some external source - whether it be crowding from a background object, light from the sky, or an extra component in the system that is unaccounted for in the system hierarchy.
To see this we'll compare a light curve with and without "third" light.
Step6:  As expected, adding 5 W/m^3 of third light simply shifts the light curve up by that exact same amount.
Step7:  Influence on Meshes (Intensities)
"Third" light does not affect the intensities stored in the mesh (including those in relative units).  In other words, like distance, "third" light only scales the fluxes.
NOTE
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Python Code:
!pip install -I "phoebe>=2.0,<2.1"
Explanation: "Third" Light
Setup
Let's first make sure we have the latest version of PHOEBE 2.0 installed. (You can comment out this line if you don't use pip for your installation or don't want to update to the latest release).
End of explanation
%matplotlib inline
import phoebe
from phoebe import u # units
import numpy as np
import matplotlib.pyplot as plt
logger = phoebe.logger()
b = phoebe.default_binary()
Explanation: As always, let's do imports and initialize a logger and a new bundle.  See Building a System for more details.
End of explanation
b.filter(qualifier='l3')
Explanation: Relevant Parameters
The 'l3' parameter describes how much third light exists in a given passband.  Since this is passband dependent and only used for flux measurments - it does not yet exist for a new empty Bundle.
End of explanation
b.add_dataset('lc', times=np.linspace(0,1,101), dataset='lc01')
Explanation: So let's add a LC dataset
End of explanation
b.filter(qualifier='l3')
print b['l3@lc01']
Explanation: We now see that the LC dataset created an 'l3' parameters for the new dataset.
End of explanation
b.run_compute(irrad_method='none', model='no_third_light')
b['l3@lc01'] = 5
b.run_compute(irrad_method='none', model='with_third_light')
Explanation: Influence on Light Curves (Fluxes)
"Third" light is simply additional flux added to the light curve from some external source - whether it be crowding from a background object, light from the sky, or an extra component in the system that is unaccounted for in the system hierarchy.
To see this we'll compare a light curve with and without "third" light.
End of explanation
fig = plt.figure()
ax1, ax2 = fig.add_subplot(121), fig.add_subplot(122)
axs, artists = b['lc01'].plot(model='no_third_light', ax=ax1)
axs, artists = b['lc01'].plot(model='with_third_light', ax=ax2)
Explanation: As expected, adding 5 W/m^3 of third light simply shifts the light curve up by that exact same amount.
End of explanation
b.add_dataset('mesh', times=[0], dataset='mesh01')
b['l3@lc01'] = 0.0
b.run_compute(irrad_method='none', model='no_third_light')
b['l3@lc01'] = 5
b.run_compute(irrad_method='none', model='with_third_light')
print "no_third_light abs_intensities: ", b.get_value(qualifier='abs_intensities', component='primary', dataset='lc01', model='no_third_light').mean()
print "with_third_light abs_intensities: ", b.get_value(qualifier='abs_intensities', component='primary', dataset='lc01', model='with_third_light').mean()
print "no_third_light intensities: ", b.get_value(qualifier='intensities', component='primary', dataset='lc01', model='no_third_light').mean()
print "with_third_light intensities: ", b.get_value(qualifier='intensities', component='primary', dataset='lc01', model='with_third_light').mean()
Explanation: Influence on Meshes (Intensities)
"Third" light does not affect the intensities stored in the mesh (including those in relative units).  In other words, like distance, "third" light only scales the fluxes.
NOTE: this is different than pblums which DO affect the relative intensities.  Again, see the pblum tutorial for more details.
To see this we can run both of our models again and look at the values of the intensities in the mesh.
End of explanation
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