Implement `__str__` for `plan7.Alignment` using `p7_nontranslated_alidisplay_Print`

include/libhmmer/p7_alidisplay.pxd

@@ -12,6 +12,13 @@ ELIF HMMER_IMPL == "SSE":
     from libhmmer.impl_sse.p7_oprofile cimport P7_OPROFILE
 
 
+cdef extern from "hmmer.h" nogil:
+
+    cdef struct p7_pipeline:
+        pass
+    ctypedef p7_pipeline P7_PIPELINE
+
+
 cdef extern from "hmmer.h" nogil:
 
     cdef struct p7_alidisplay_s:
@@ -56,11 +63,14 @@ cdef extern from "hmmer.h" nogil:
     float          p7_alidisplay_DecodePostProb(char pc);
     char           p7_alidisplay_EncodeAliPostProb(float p, float hi, float med, float lo);
 
-    # int            p7_alidisplay_Print(FILE *fp, P7_ALIDISPLAY *ad, int min_aliwidth, int linewidth, P7_PIPELINE *pli);
-    # int            p7_translated_alidisplay_Print(FILE *fp, P7_ALIDISPLAY *ad, int min_aliwidth, int linewidth, P7_PIPELINE *pli);
-    int            p7_nontranslated_alidisplay_Print(FILE *fp, P7_ALIDISPLAY *ad, int min_aliwidth, int linewidth, int show_accessions);
-
     int            p7_alidisplay_Backconvert(const P7_ALIDISPLAY *ad, const ESL_ALPHABET *abc, ESL_SQ **ret_sq, P7_TRACE **ret_tr);
     int            p7_alidisplay_Sample(ESL_RANDOMNESS *rng, int N, P7_ALIDISPLAY **ret_ad);
     int            p7_alidisplay_Dump(FILE *fp, const P7_ALIDISPLAY *ad);
     int            p7_alidisplay_Compare(const P7_ALIDISPLAY *ad1, const P7_ALIDISPLAY *ad2);
+
+# The GIL may be held there in case the FILE* is a Python file object
+cdef extern from "hmmer.h":
+
+    int            p7_alidisplay_Print(FILE *fp, P7_ALIDISPLAY *ad, int min_aliwidth, int linewidth, P7_PIPELINE *pli);
+    int            p7_translated_alidisplay_Print(FILE *fp, P7_ALIDISPLAY *ad, int min_aliwidth, int linewidth, P7_PIPELINE *pli);
+    int            p7_nontranslated_alidisplay_Print(FILE *fp, P7_ALIDISPLAY *ad, int min_aliwidth, int linewidth, int show_accessions);

pyhmmer/plan7.pyx

@@ -206,6 +206,31 @@ cdef class Alignment:
     def __len__(self):
         return self.hmm_to - self.hmm_from
 
+    def __str__(self):
+        assert self._ad != NULL
+
+        cdef int    status
+        cdef object buffer = io.BytesIO()
+        cdef FILE*  fp     = fopen_obj(buffer, "w")
+
+        try:
+            status = libhmmer.p7_alidisplay.p7_nontranslated_alidisplay_Print(
+                fp,
+                self._ad,
+                0,
+                -1,
+                False,
+            )
+            if status == libeasel.eslEWRITE:
+                raise OSError("Failed to write alignment")
+            elif status != libeasel.eslOK:
+                raise UnexpectedError(status, "p7_alidisplay_Print")
+        finally:
+            fclose(fp)
+
+        return buffer.getvalue().decode("ascii")
+
+
     # --- Properties ---------------------------------------------------------
 
     @property
@@ -993,7 +1018,7 @@ cdef class Cutoffs:
         c._owner = self._owner
         return c
 
-    def __str__(self):
+    def __repr__(self):
         ty = type(self).__name__
         return "<Pfam score cutoffs of {!r}>".format(
             self._owner,
@@ -1403,7 +1428,7 @@ cdef class EvalueParameters:
         ev._evparams = self._evparams
         return ev
 
-    def __str__(self):
+    def __repr__(self):
         ty = type(self).__name__
         return "<e-value parameters of {!r}>".format(
             self._owner,