docs: add code samples for Series.{between, cumprod} (#353)

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- [x] Appropriate docs were updated (if necessary)
     - [x] `Series.between()`: https://screenshot.googleplex.com/BhHpZsL7S9d3FsG
     - [x] `Series.cumprod()`: https://screenshot.googleplex.com/7o7gDNwJZEWst84

Fixes #<issue_number_goes_here> 🦕

third_party/bigframes_vendored/pandas/core/series.py

@@ -1777,6 +1777,42 @@ def between(
         corresponding Series element is between the boundary values `left` and
         `right`. NA values are treated as `False`.
 
+        **Examples:**
+
+            >>> import bigframes.pandas as bpd
+            >>> bpd.options.display.progress_bar = None
+
+        Boundary values are included by default:
+
+            >>> s = bpd.Series([2, 0, 4, 8, np.nan])
+            >>> s.between(1, 4)
+            0     True
+            1    False
+            2     True
+            3    False
+            4     <NA>
+            dtype: boolean
+
+        With inclusive set to "neither" boundary values are excluded:
+
+            >>> s.between(1, 4, inclusive="neither")
+            0     True
+            1    False
+            2    False
+            3    False
+            4     <NA>
+            dtype: boolean
+
+        left and right can be any scalar value:
+
+            >>> s = bpd.Series(['Alice', 'Bob', 'Carol', 'Eve'])
+            >>> s.between('Anna', 'Daniel')
+            0    False
+            1     True
+            2     True
+            3    False
+            dtype: boolean
+
         Args:
             left (scalar or list-like):
                 Left boundary.
@@ -1799,6 +1835,30 @@ def cumprod(self):
         Returns a DataFrame or Series of the same size containing the cumulative
         product.
 
+        **Examples:**
+
+            >>> import bigframes.pandas as bpd
+            >>> bpd.options.display.progress_bar = None
+
+            >>> s = bpd.Series([2, np.nan, 5, -1, 0])
+            >>> s
+            0     2.0
+            1    <NA>
+            2     5.0
+            3    -1.0
+            4     0.0
+            dtype: Float64
+
+        By default, NA values are ignored.
+
+            >>> s.cumprod()
+            0     2.0
+            1    <NA>
+            2    10.0
+            3   -10.0
+            4     0.0
+            dtype: Float64
+
         Returns:
             bigframes.series.Series: Return cumulative sum of scalar or Series.
         """