Rearrange Variant* class documentation

Author: jmarshall

doc/api.rst

@@ -213,28 +213,37 @@ VCF/BCF files
 .. autoclass:: pysam.VariantHeader
    :members:
 
-.. autoclass:: pysam.VariantHeaderMetadata
+.. autoclass:: pysam.VariantRecord
    :members:
 
-.. autoclass:: pysam.VariantMetadata
+.. autoclass:: pysam.VariantContig
    :members:
 
-.. autoclass:: pysam.VariantHeaderRecords
+.. autoclass:: pysam.VariantHeaderRecord
    :members:
 
-.. autoclass:: pysam.VariantHeaderRecord
+.. autoclass:: pysam.VariantMetadata
+   :members:
+
+.. autoclass:: pysam.VariantRecordSample
    :members:
 
+Internal classes
+----------------
+
+These classes are used internally to represent particular header and record
+fields. They cannot be instantiated directly in your Python or Cython code.
+
 .. autoclass:: pysam.VariantHeaderContigs
    :members:
 
-.. autoclass:: pysam.VariantContig
+.. autoclass:: pysam.VariantHeaderMetadata
    :members:
 
-.. autoclass:: pysam.VariantHeaderSamples
+.. autoclass:: pysam.VariantHeaderRecords
    :members:
 
-.. autoclass:: pysam.VariantRecord
+.. autoclass:: pysam.VariantHeaderSamples
    :members:
 
 .. autoclass:: pysam.VariantRecordFilter
@@ -249,8 +258,6 @@ VCF/BCF files
 .. autoclass:: pysam.VariantRecordSamples
    :members:
 
-.. autoclass:: pysam.VariantRecordSample
-   :members:
 
 HTSFile
 =======