Fix Codacy Warnings (#477)

---------

Co-authored-by: Dario Coscia <dariocos99@gmail.com>

pina/utils.py

@@ -1,26 +1,40 @@
 """Utils module."""
 
 import types
+from functools import reduce
 import torch
 
-from functools import reduce
 from .label_tensor import LabelTensor
 
 
+# Codacy error unused parameters
 def custom_warning_format(
     message, category, filename, lineno, file=None, line=None
 ):
+    """
+    Depewarning custom format.
+
+    :param str message: The warning message.
+    :param class category: The warning category.
+    :param str filename: The filename where the warning was raised.
+    :param int lineno: The line number where the warning was raised.
+    :param str file: The file object where the warning was raised.
+    :param inr line: The line where the warning was raised.
+    :return: The formatted warning message.
+    :rtype: str
+    """
     return f"{filename}: {category.__name__}: {message}\n"
 
 
-def check_consistency(object, object_instance, subclass=False):
+def check_consistency(object_, object_instance, subclass=False):
     """Helper function to check object inheritance consistency.
        Given a specific ``'object'`` we check if the object is
        instance of a specific ``'object_instance'``, or in case
        ``'subclass=True'`` we check if the object is subclass
        if the ``'object_instance'``.
 
-    :param (iterable or class object) object: The object to check the inheritance
+    :param (iterable or class object) object: The object to check the
+        inheritance
     :param Object object_instance: The parent class from where the object
         is expected to inherit
     :param str object_name: The name of the object
@@ -28,17 +42,19 @@ def check_consistency(object, object_instance, subclass=False):
     :raises ValueError: If the object does not inherit from the
         specified class
     """
-    if not isinstance(object, (list, set, tuple)):
-        object = [object]
+    if not isinstance(object_, (list, set, tuple)):
+        object_ = [object_]
 
-    for obj in object:
+    for obj in object_:
         try:
             if not subclass:
                 assert isinstance(obj, object_instance)
             else:
                 assert issubclass(obj, object_instance)
-        except AssertionError:
-            raise ValueError(f"{type(obj).__name__} must be {object_instance}.")
+        except AssertionError as e:
+            raise ValueError(
+                f"{type(obj).__name__} must be {object_instance}."
+            ) from e
 
 
 def labelize_forward(forward, input_variables, output_variables):
@@ -67,12 +83,14 @@ def labelize_forward(forward, input_variables, output_variables):
 
 
 def merge_tensors(tensors):  # name to be changed
+    """TODO"""
     if tensors:
         return reduce(merge_two_tensors, tensors[1:], tensors[0])
     raise ValueError("Expected at least one tensor")
 
 
 def merge_two_tensors(tensor1, tensor2):
+    """TODO"""
     n1 = tensor1.shape[0]
     n2 = tensor2.shape[0]
 
@@ -125,7 +143,7 @@ def is_function(f):
     :return: `True` if `f` is a function, `False` otherwise.
     :rtype: bool
     """
-    return type(f) == types.FunctionType or type(f) == types.LambdaType
+    return isinstance(f, (types.FunctionType, types.LambdaType))
 
 
 def chebyshev_roots(n):