Fix docstrings

Fixed some docstrings.

chess/__init__.py

@@ -3660,25 +3660,25 @@ def __len__(self) -> int:
     # MutableSet
 
     def add(self, square: Square) -> None:
-        """Adds a square to the set."""
+        """Adds a square to a set."""
         self.mask |= BB_SQUARES[square]
 
     def discard(self, square: Square) -> None:
-        """Discards a square from the set."""
+        """Discards a square from a set."""
         self.mask &= ~BB_SQUARES[square]
 
     # frozenset
 
     def isdisjoint(self, other: IntoSquareSet) -> bool:
-        """Test if the square sets are disjoint."""
+        """Tests if square sets are disjoint."""
         return not bool(self & other)
 
     def issubset(self, other: IntoSquareSet) -> bool:
-        """Test if this square set is a subset of another."""
+        """Tests if this square set is a subset of another."""
         return not bool(~self & other)
 
     def issuperset(self, other: IntoSquareSet) -> bool:
-        """Test if this square set is a superset of another."""
+        """Tests if this square set is a superset of another."""
         return not bool(self & ~SquareSet(other))
 
     def union(self, other: IntoSquareSet) -> SquareSet:
@@ -3750,9 +3750,9 @@ def __ixor__(self, other: IntoSquareSet) -> SquareSet:
 
     def remove(self, square: Square) -> None:
         """
-        Removes a square from the set.
+        Removes the given *square* from a set.
 
-        :raises: :exc:`KeyError` if the given square was not in the set.
+        :raises: :exc:`KeyError` if the given square was not in a set.
         """
         mask = BB_SQUARES[square]
         if self.mask & mask:
@@ -3762,7 +3762,7 @@ def remove(self, square: Square) -> None:
 
     def pop(self) -> Square:
         """
-        Removes a square from the set and returns it.
+        Removes a square from a set and returns it.
 
         :raises: :exc:`KeyError` on an empty set.
         """
@@ -3774,21 +3774,21 @@ def pop(self) -> Square:
         return square
 
     def clear(self) -> None:
-        """Remove all elements from this set."""
+        """Removes all elements from this set."""
         self.mask = BB_EMPTY
 
     # SquareSet
 
     def carry_rippler(self) -> Iterator[Bitboard]:
-        """Iterator over the subsets of this set."""
+        """Iterates over subsets of this set."""
         return _carry_rippler(self.mask)
 
     def mirror(self) -> SquareSet:
         """Returns a vertically mirrored copy of this square set."""
         return SquareSet(flip_vertical(self.mask))
 
     def tolist(self) -> List[bool]:
-        """Convert the set to a list of 64 bools."""
+        """Converts a set to a list of 64 bools."""
         result = [False] * 64
         for square in self:
             result[square] = True
@@ -3850,7 +3850,7 @@ def _repr_svg_(self) -> str:
     @classmethod
     def ray(cls, a: Square, b: Square) -> SquareSet:
         """
-        All squares on the rank, file or diagonal with the two squares, if they
+        Marks all squares on the rank, file or diagonal with the two squares, if they
         are aligned.
 
         >>> import chess
@@ -3870,7 +3870,7 @@ def ray(cls, a: Square, b: Square) -> SquareSet:
     @classmethod
     def between(cls, a: Square, b: Square) -> SquareSet:
         """
-        All squares on the rank, file or diagonal between the two squares
+        Marks all squares on the rank, file or diagonal between the two squares
         (bounds not included), if they are aligned.
 
         >>> import chess