added information on accessing docstrings

doc/python.tex

@@ -33,6 +33,40 @@ import mitsuba
 For an overview of the currently exposed API subset, please refer
 to the following page: \url{http://www.mitsuba-renderer.org/api/group__libpython.html}.
 
+\subsubsection{Accessing signatures in an interactive Python shell}
+The plugin exports comprehensive Python-style docstrings, hence
+the following is an alternative and convenient way of getting information on
+classes, function, or entire namespaces when running an interactive Python shell.
+\begin{shell}
+>>> help(mitsuba.core.Bitmap) # (can be applied to namespaces, classes, functions, etc.)
+
+ class Bitmap(Object)
+  |  Method resolution order:
+  |      Bitmap
+  |      Object
+  |      Boost.Python.instance
+  |      __builtin__.object
+  |
+  |  Methods defined here:
+  |  __init__(...)
+  |      __init__( (object)arg1, (EPixelFormat)arg2, (EComponentFormat)arg3, (Vector2i)arg4) -> None :
+  |          C++ signature :
+  |              void __init__(_object*,mitsuba::Bitmap::EPixelFormat,mitsuba::Bitmap::EComponentFormat,mitsuba::TVector2<int>)
+  |
+  |      __init__( (object)arg1, (EFileFormat)arg2, (Stream)arg3) -> None :
+  |          C++ signature :
+  |              void __init__(_object*,mitsuba::Bitmap::EFileFormat,mitsuba::Stream*)
+  |
+  |  clear(...)
+  |      clear( (Bitmap)arg1) -> None :
+  |          C++ signature :
+  |              void clear(mitsuba::Bitmap {lvalue})
+...
+\end{shell}
+The docstrings list the currently exported functionality, as well as C++ and Python signatures, but they
+don't document what these functions actually do. The web API documentation is the preferred source for
+this information.
+
 \subsection{Basics}
 Generally, the Python API tries to mimic the C++ API as closely as possible.
 Where applicable, the Python classes and methods replicate overloaded operators,