Documentation for v0.1 version (#199)

* Adding Equations, solving typos
* improve _code.rst
* the team rst and restuctore index.rst
* fixing errors

---------

Co-authored-by: Dario Coscia <dariocoscia@dhcp-015.eduroam.sissa.it>

tests/test_condition.py

@@ -1,17 +1,19 @@
 import torch
 import pytest
 
-from pina import LabelTensor, Condition, CartesianDomain, PINN
+from pina import LabelTensor, Condition
+from pina.solvers import PINN
+from pina.geometry import CartesianDomain
 from pina.problem import SpatialProblem
 from pina.model import FeedForward
 from pina.operators import laplacian
 from pina.equation.equation_factory import FixedValue
 
-
 example_domain = CartesianDomain({'x': [0, 1], 'y': [0, 1]})
 example_input_pts = LabelTensor(torch.tensor([[0, 0, 0]]), ['x', 'y', 'z'])
 example_output_pts = LabelTensor(torch.tensor([[1, 2]]), ['a', 'b'])
 
+
 def test_init_inputoutput():
     Condition(input_points=example_input_pts, output_points=example_output_pts)
     with pytest.raises(ValueError):
@@ -21,8 +23,9 @@ def test_init_inputoutput():
     with pytest.raises(TypeError):
         Condition(input_points=example_domain, output_points=example_domain)
 
+
 def test_init_locfunc():
-    Condition(location=example_domain, equation=FixedValue(0.0))    
+    Condition(location=example_domain, equation=FixedValue(0.0))
     with pytest.raises(ValueError):
         Condition(example_domain, FixedValue(0.0))
     with pytest.raises(TypeError):
@@ -30,6 +33,7 @@ def test_init_locfunc():
     with pytest.raises(TypeError):
         Condition(location=example_input_pts, equation=example_output_pts)
 
+
 def test_init_inputfunc():
     Condition(input_points=example_input_pts, equation=FixedValue(0.0))
     with pytest.raises(ValueError):