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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:
 PythonFMU example
This is an example on how to use PythonFMU in order to export a Python script as a FMI 2.0 for CoSimulation compliant FMU.
Installation
But first thing first, you will need the pythonfmu Python package. To install it, you can use the pip package manager
Step1:  Generate the FMU
The FMU is generated through the command line tool pythonfmu build.
Step2:  The mandatory information to pass to the builder is the Python script file through the -f option. 
By default the generated FMU states that a external tool (i.e. Python) is needed for its execution. But the usage of the FMU is demonstrated through pyfmi that does not support that feature. This is the reason the option --no-external-tool is provided.
The full list of available options is
Step3:  Use the FMU
You can now use the FMU. For example through the pyfmi Python package
Step4:  The code specifies a parameter, which you could change
Step5:  Install FMU dependencies
Python script can use third-party libraries. PythonFMU does not include such dependencies within the FMU. So it is up to the end user to installed the dependent packages.
However to help the process, you could include as project file in your FMU a requirement file. Then the end user will be able to install the dependencies using the pythonfmu deploy tool. The tool supports for now two packages manager
Step6:  Include the requirement file
Step7:  Installation by the end user
scipy is not yet installed. So the FMU cannot be executed.
Step8:  To install the FMU dependencies, the end user will need to execute
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Python Code:
%pycat demoslave.py
Explanation: PythonFMU example
This is an example on how to use PythonFMU in order to export a Python script as a FMI 2.0 for CoSimulation compliant FMU.
Installation
But first thing first, you will need the pythonfmu Python package. To install it, you can use the pip package manager:
bash
python -m pip install pythonfmu
The to-be-exported script
To export Python code as FMU, you will need to interface your code with the FMI facade provided through an abstract class pythonfmu.Fmi2Slave.
In the following example, you will interface a simple resistor code.
End of explanation
!pythonfmu build -f ./demoslave.py --no-external-tool
Explanation: Generate the FMU
The FMU is generated through the command line tool pythonfmu build.
End of explanation
!pythonfmu build -h
Explanation: The mandatory information to pass to the builder is the Python script file through the -f option. 
By default the generated FMU states that a external tool (i.e. Python) is needed for its execution. But the usage of the FMU is demonstrated through pyfmi that does not support that feature. This is the reason the option --no-external-tool is provided.
The full list of available options is:
End of explanation
%matplotlib inline
from pyfmi import load_fmu
import matplotlib.pyplot as p
import numpy
model = load_fmu('Resistor.fmu')
inputs = ('positive_pin_v', lambda t: 20 + 5. * numpy.cos(t))
res = model.simulate(final_time=30, input=inputs, options={'ncp': 300})
fig = p.figure()
ax1 = p.subplot(2, 1, 1)
ax1.plot(res['time'], res['i'])
ax1.set_ylabel('Intensity [A]')
ax2 = p.subplot(2, 1, 2)
ax2.plot(res['time'], res['delta_v'])
ax2.set_xlabel('time')
ax2.set_ylabel('Voltage [V]')
p.show();
Explanation: Use the FMU
You can now use the FMU. For example through the pyfmi Python package:
End of explanation
R_reference = model.get_model_variables()['R'].value_reference
model.set_real([R_reference, ], [1000., ])
res2 = model.simulate(final_time=30, input=inputs, options={'ncp': 300})
fig = p.figure()
p.plot(res['time'], res['i'], res2['time'], res2['i'])
p.xlabel('time')
p.ylabel('Voltage [V]')
p.show();
model.free_instance()  # It is currently not possible to load two Python FMUs simultaneously
Explanation: The code specifies a parameter, which you could change:
End of explanation
!pythonfmu deploy -h
Explanation: Install FMU dependencies
Python script can use third-party libraries. PythonFMU does not include such dependencies within the FMU. So it is up to the end user to installed the dependent packages.
However to help the process, you could include as project file in your FMU a requirement file. Then the end user will be able to install the dependencies using the pythonfmu deploy tool. The tool supports for now two packages manager: pip and conda. Moreover if you use the default convention for naming the requirement file (i.e. requirements.txt for pip and environment.yml for conda), the end user won't need to specify the file name nor the package manager to be used.
In the following paragraphs, an example requiring scipy will be demonstated. The Python facade is defined in the scipyslave.py file and the requirement are provided in environment.yml for usage with conda.
End of explanation
!pythonfmu build -f sympyslave.py environment.yml --no-external-tool
Explanation: Include the requirement file
End of explanation
%matplotlib inline
from pyfmi import load_fmu
import matplotlib.pyplot as p
import numpy
sympy_model = load_fmu('SympySlave.fmu')
inputs = ('realIn', lambda t: 5.)
sympy_model.simulate(final_time=30, input=inputs, options={'ncp': 300});
Explanation: Installation by the end user
scipy is not yet installed. So the FMU cannot be executed.
End of explanation
!pythonfmu deploy -f SympySlave.fmu
Explanation: To install the FMU dependencies, the end user will need to execute:
End of explanation
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