Add missing pylibcudf strings docs (#16471)

Noticed a few missing pylibcudf string docs that were missed, added them here.

Authors:
  - https://github.com/brandon-b-miller
  - Thomas Li (https://github.com/lithomas1)

Approvers:
  - Thomas Li (https://github.com/lithomas1)

URL: #16471

docs/cudf/source/user_guide/api_docs/pylibcudf/strings/capitalize.rst

@@ -0,0 +1,6 @@
+==========
+capitalize
+==========
+
+.. automodule:: cudf._lib.pylibcudf.strings.capitalize
+   :members:

docs/cudf/source/user_guide/api_docs/pylibcudf/strings/char_types.rst

@@ -0,0 +1,6 @@
+==========
+char_types
+==========
+
+.. automodule:: cudf._lib.pylibcudf.strings.char_types
+   :members:

docs/cudf/source/user_guide/api_docs/pylibcudf/strings/find.rst

@@ -0,0 +1,6 @@
+====
+find
+====
+
+.. automodule:: cudf._lib.pylibcudf.strings.find
+   :members:

docs/cudf/source/user_guide/api_docs/pylibcudf/strings/index.rst

@@ -4,6 +4,11 @@ strings
 .. toctree::
     :maxdepth: 1
 
+    capitalize
+    char_types
     contains
+    find
+    regex_flags
+    regex_program
     replace
     slice

docs/cudf/source/user_guide/api_docs/pylibcudf/strings/regex_flags.rst

@@ -0,0 +1,6 @@
+===========
+regex_flags
+===========
+
+.. automodule:: cudf._lib.pylibcudf.strings.regex_flags
+   :members:

docs/cudf/source/user_guide/api_docs/pylibcudf/strings/regex_program.rst

@@ -0,0 +1,6 @@
+=============
+regex_program
+=============
+
+.. automodule:: cudf._lib.pylibcudf.strings.regex_program
+   :members:

python/cudf/cudf/_lib/pylibcudf/strings/capitalize.pyx

@@ -22,7 +22,22 @@ cpdef Column capitalize(
     # TODO: default scalar values
     # https://github.com/rapidsai/cudf/issues/15505
 ):
-
+    """Returns a column of capitalized strings.
+
+    For details, see :cpp:func:`cudf::strings::capitalize`.
+
+    Parameters
+    ----------
+    input : Column
+        String column
+    delimiters : Scalar, default None
+        Characters for identifying words to capitalize
+
+    Returns
+    -------
+    pylibcudf.Column
+        Column of strings capitalized from the input column
+    """
     cdef unique_ptr[column] c_result
 
     if delimiters is None:
@@ -47,6 +62,23 @@ cpdef Column title(
     Column input,
     string_character_types sequence_type=string_character_types.ALPHA
 ):
+    """Modifies first character of each word to upper-case and lower-cases
+    the rest.
+
+    For details, see :cpp:func:`cudf::strings::title`.
+
+    Parameters
+    ----------
+    input : Column
+        String column
+    sequence_type : string_character_types, default string_character_types.ALPHA
+        The character type that is used when identifying words
+
+    Returns
+    -------
+    pylibcudf.Column
+        Column of titled strings
+    """
     cdef unique_ptr[column] c_result
     with nogil:
         c_result = cpp_capitalize.title(input.view(), sequence_type)
@@ -55,6 +87,20 @@ cpdef Column title(
 
 
 cpdef Column is_title(Column input):
+    """Checks if the strings in the input column are title formatted.
+
+    For details, see :cpp:func:`cudf::strings::is_title`.
+
+    Parameters
+    ----------
+    input : Column
+        String column
+
+    Returns
+    -------
+    pylibcudf.Column
+        Column of type BOOL8
+    """
     cdef unique_ptr[column] c_result
     with nogil:
         c_result = cpp_capitalize.is_title(input.view())

python/cudf/cudf/_lib/pylibcudf/strings/regex_program.pyx

@@ -13,12 +13,31 @@ from cudf._lib.pylibcudf.strings.regex_flags cimport regex_flags
 
 
 cdef class RegexProgram:
+    """Regex program class.
 
+    This is the Cython representation of
+    :cpp:class:`cudf::strings::regex_program`.
+
+    Do not instantiate this class directly, use the `create` method.
+
+    """
     def __init__(self, *args, **kwargs):
         raise ValueError("Do not instantiate RegexProgram directly, use create")
 
     @staticmethod
     def create(str pattern, int flags):
+        """Create a program from a pattern.
+
+        For detils, see :cpp:func:`cudf::strings::regex_program::create`.
+
+        Parameters
+        ----------
+        pattern : str
+            Regex pattern
+        flags : Uniont[int, RegexFlags]
+            Regex flags for interpreting special characters in the pattern
+
+        """
         cdef unique_ptr[regex_program] c_prog
         cdef regex_flags c_flags
         cdef string c_pattern = pattern.encode()