Add isin examples in Docstring (#7479)

Fully resolves: #7412 

Most of the fix to address #7412 were done as part of pandas upgrade in #7375. This PR only includes docstrings update to `isin`.

Authors:
  - GALI PREM SAGAR (@galipremsagar)

Approvers:
  - Keith Kraus (@kkraus14)

URL: #7479

python/cudf/cudf/core/dataframe.py

@@ -5713,6 +5713,43 @@ def isin(self, values):
         DataFrame:
             DataFrame of booleans showing whether each element in
             the DataFrame is contained in values.
+
+        Examples
+        --------
+        >>> import cudf
+        >>> df = cudf.DataFrame({'num_legs': [2, 4], 'num_wings': [2, 0]},
+        ...                     index=['falcon', 'dog'])
+        >>> df
+                num_legs  num_wings
+        falcon         2          2
+        dog            4          0
+
+        When ``values`` is a list check whether every value in the DataFrame
+        is present in the list (which animals have 0 or 2 legs or wings)
+
+        >>> df.isin([0, 2])
+                num_legs  num_wings
+        falcon      True       True
+        dog        False       True
+
+        When ``values`` is a dict, we can pass values to check for each
+        column separately:
+
+        >>> df.isin({'num_wings': [0, 3]})
+                num_legs  num_wings
+        falcon     False      False
+        dog        False       True
+
+        When ``values`` is a Series or DataFrame the index and column must
+        match. Note that 'falcon' does not match based on the number of legs
+        in other.
+
+        >>> other = cudf.DataFrame({'num_legs': [8, 2], 'num_wings': [0, 2]},
+        ...                         index=['spider', 'falcon'])
+        >>> df.isin(other)
+                num_legs  num_wings
+        falcon      True       True
+        dog        False      False
         """
 
         if isinstance(values, dict):

python/cudf/cudf/core/frame.py

@@ -239,6 +239,7 @@ def copy(self: T, deep: bool = True) -> T:
         -------
         copy : Series or DataFrame
             Object type matches caller.
+
         Examples
         --------
         >>> s = cudf.Series([1, 2], index=["a", "b"])

python/cudf/cudf/core/index.py

@@ -1362,6 +1362,16 @@ def isin(self, values):
         is_contained : cupy array
             CuPy array of boolean values.
 
+        Examples
+        --------
+        >>> idx = cudf.Index([1,2,3])
+        >>> idx
+        Int64Index([1, 2, 3], dtype='int64')
+
+        Check whether each index value in a list of values.
+
+        >>> idx.isin([1, 4])
+        array([ True, False, False])
         """
 
         result = self.to_series().isin(values).values

python/cudf/cudf/core/multiindex.py

@@ -655,16 +655,42 @@ def isin(self, values, level=None):
         level : str or int, optional
             Name or position of the index level to use (if the index
             is a MultiIndex).
+
         Returns
         -------
         is_contained : cupy array
             CuPy array of boolean values.
+
         Notes
         -------
         When `level` is None, `values` can only be MultiIndex, or a
         set/list-like tuples.
         When `level` is provided, `values` can be Index or MultiIndex,
         or a set/list-like tuples.
+
+        Examples
+        --------
+        >>> import cudf
+        >>> import pandas as pd
+        >>> midx = cudf.from_pandas(pd.MultiIndex.from_arrays([[1,2,3],
+        ...                                  ['red', 'blue', 'green']],
+        ...                                  names=('number', 'color')))
+        >>> midx
+        MultiIndex([(1,   'red'),
+                    (2,  'blue'),
+                    (3, 'green')],
+                   names=['number', 'color'])
+
+        Check whether the strings in the 'color' level of the MultiIndex
+        are in a list of colors.
+
+        >>> midx.isin(['red', 'orange', 'yellow'], level='color')
+        array([ True, False, False])
+
+        To check across the levels of a MultiIndex, pass a list of tuples:
+
+        >>> midx.isin([(1, 'red'), (3, 'red')])
+        array([ True, False, False])
         """
         from cudf.utils.dtypes import is_list_like
 

python/cudf/cudf/core/series.py

@@ -3784,6 +3784,41 @@ def isin(self, values):
         -------
         TypeError
             If values is a string
+
+        Examples
+        --------
+        >>> import cudf
+        >>> s = cudf.Series(['lama', 'cow', 'lama', 'beetle', 'lama',
+        ...                'hippo'], name='animal')
+        >>> s.isin(['cow', 'lama'])
+        0     True
+        1     True
+        2     True
+        3    False
+        4     True
+        5    False
+        Name: animal, dtype: bool
+
+        Passing a single string as ``s.isin('lama')`` will raise an error. Use
+        a list of one element instead:
+
+        >>> s.isin(['lama'])
+        0     True
+        1    False
+        2     True
+        3    False
+        4     True
+        5    False
+        Name: animal, dtype: bool
+
+        Strings and integers are distinct and are therefore not comparable:
+
+        >>> cudf.Series([1]).isin(['1'])
+        0    False
+        dtype: bool
+        >>> cudf.Series([1.1]).isin(['1.1'])
+        0    False
+        dtype: bool
         """
 
         if is_scalar(values):